[b][color=#008000][size=5]My personal opinion on good AddOns[/size][/color][/b]
[color=#ffa500][b]Unit Frames[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/pitbull4"]PitBull Unit Frames[/url][/td][td]Very detailed unit frames, allows many options.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/simple-unit-frames"]Simple Unit Frames[/url][/td][td]More detailed version of the standard WoW unit frames.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/shadowed-unit-frames"]Shadowed Unit Frames[/url][/td][td]Less complicated version of PitBull.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/xperl"]X-Perl Unit Frames[/url][/td][td]My personal favourite unit frame AddOn as it is easy to configure and shows detailed information on the target.[/td][/tr][/table]
[color=#008080][b]Raid and Party Frames[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/clique"]Clique[/url][/td][td]Allows click- and hover-casting on unit, raid and party frames.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/grid2"]Grid2[/url][/td][td]Shows raid or party and is very accurate about health and mana.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/heal-bot-continued"]HealBot Continued[/url][/td][td]Same thing as VuhDo but allows you to use all the buttons on your mouse including all the buttons on the the razor naga mouse.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/vuhdo"]VuhDo[/url][/td][td]Shows people in your group and raid and also allows you to click the name to cast a spell on that target, allows many more options.[/td][/tr][/table]
[color=#ff6666][b]Nameplates[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/tidy-plates"]Tidy Plates[/url][/td][td]Near square nameplates, customisation options, and look good with basic minimap.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/healers-have-to-die"]Healers have to die[/url][/td][td]Adds two different healer symbols to the nameplates of friendly and enemy healers.[/td][/tr][/table]
[color=#008000][b]Action Bars[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/bartender4"]Bartender[/url][/td][td]My personal favourite as it's easy to configure and allows a lot of options.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/dominos"]Dominos[/url][/td][td]Less detailed version of Bartender.[/td][/tr][/table]
[color=#ffa500][b]Casting Bars[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/quartz"]Quartz[/url][/td][td]Shows spell time.[/td][/tr][/table]
[color=#008080][b]Minimap[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/basic-minimap"]Basic Minimap[/url][/td][td]Square map and my personal favourite.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/chinchilla"]Chinchilla Minimap[/url][/td][td]Allows you to choose the appearance of the map from a few options and comes with coordinates.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/dominos_minimap?page=2"]Dominos Minimap[/url][/td][td]Square map.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/minimap-button-frame"]Minimap Button Frame[/url][/td][td]Collects minimap buttons for easy access and minimal clutter.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/sexymap"]Sexy Map[/url][/td][td]Border for your minimap.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/simple-minimap"]Simple Minimap[/url][/td][td]Allows you to choose the appearance of the map from a few options.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/wmmap"]wMmap[/url][/td][td]Not very detailed map but comes with configuration of the positions of worldstate, quest objectives and achievement objectives.[/td][/tr][/table]
[color=#ff6666][b]Map and Navigation[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/carbonite"]Carbonite[/url][/td][td]Has a map, minimap, quest helper and an advanced social list with your friends from other characters on the list on your other toon.[/td][/tr]
[tr][td][url="http://www.curse.com/addon-packs/wow/cartographer-replacement-7045"]Cartographer[/url][/td][td]Cartographer replacement AddOns.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/Mapster"]Mapster[/url][/td][td]More world and zone map functions.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/tomtom"]TomTom[/url][/td][td]Personal navigation assistant. I use it mainly for chest farming on 20 lvl.[/td][/tr][/table]
[color=#008000][b]PvP - Communication[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/bg-defender"]BG Defender[/url][/td][td]Helps you quickly call out # of incoming/help needed/safe in BGs, if you are near a point to defend.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/cant-heal-you"]Can't Heal You[/url][/td][td]/W's the person you are trying to heal if they are out of range or line sight to tell them that they are out of range or line sight.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/focusheals"]focusheals[/url][/td][td]Type /fh b to announce a list of the enemy healers in /bg[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/saysapped"]SaySapped[/url][/td][td]Immediately /S Sapped when sapped and informs you in chat who did it.[/td][/tr][/table]
[color=#ffa500][b]PvP - Enemy Information and Timers[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/battlegroundtargets"]BattlegroundTargets[/url][/td][td]Shows the opposite faction's health and mana in a BG.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/capping-bg-timers"]Capping Battleground Timers[/url][/td][td]Shows timers in BG's and FC and EFC names in WSG and Twin Peaks.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/dbm-spelltimers"]DBM-SpellTimers[/url][/td][td]Same thing as Capping but doesn't show EFC or FC's name on the worldstate.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/spy"]Spy[/url][/td][td]Helps determine the enemy's class and spec.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/stealth-alerter"]Stealth Alerter[/url][/td][td]Shows who has used Stealth or Prowl with both factions, if you get sapped it tells you the perpetrator.[/td][/tr][/table]
[color=#008080][b]PvP and PvE Combat - Alerts, UI Mods, Spell Suggestions, Misc[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/dhud4"]DHUD4[/url][/td][td]Shows your and your target's health by the side of your character.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/GTFO"]GTFO[/url][/td][td]Sounds different alarms if you are in AoE/close to drowning/fatigue zone/etc.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/mik-scrolling-battle-text"]MikScrollingBattleText[/url][/td][td]Battle text.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/nugie-combo-bar"]NugComboBar[/url][/td][td]Shows combo points and holy power.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/omen-threat-meter"]Omen Threat Meter[/url][/td][td]Threat metre.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/poisoner"]Poisoner[/url][/td][td]Makes it easier for rogues to remember to use poison.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/PowerDing"]PowerDing[/url][/td][td]For pallies, microwave ding at full holy charge.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/range-display"]RangeDisplay[/url][/td][td]Shows the range of the target.[/td][/tr]
[tr][td][url="http://www.wowinterface.com/downloads/info15078-SnowfallKeyPress.html"]SnowfallKeyPress[/url][/td][td]Uses the key binding you have just used when you release the key.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/spell-alerter"]SpellAlerter[/url][/td][td]Alerts you of spells.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/spellflash"]SpellFlash[/url][/td][td]Suggests spells to use by making the spell icon flash. Get the appropriate [url="http://www.curse.com/search?search=SpellFlash"]class pack[/url].[/td][/tr][/table]
[color=#ff6666][b]Interrupts and Cooldowns[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/interruptbar"]InterruptBar[/url][/td][td]Shows interrupts.[/td][/tr]
[tr][td][url="http://www.wowinterface.com/downloads/info19148-Icicle.html"]Icicle[/url][/td][td]Less messy version of InterruptBar.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/losecontrol"]LoseControl[/url][/td][td]Tells you the duration of CC's.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/omni-cc"]OmniCC[/url][/td][td]Spell CD's.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/sexycooldown"]SexyCooldown[/url][/td][td]Shows cooldown remaining times on a bar. [/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/shutupfool"]Shutupfool[/url][/td][td]Silly AddOn, features Mr. T yelling "SHUT UP FOOL" when you interrupt an enemy player. Note, only you hear this.[/td][/tr][/table]
[color=#008000][b]Damage and Healing Statistics[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/recount"]Recount[/url][/td][td]Shows damage, DPS etc. of raid or party.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/skada"]Skada Damage Meter[/url][/td][td]Same as recount.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/TinyDPS"]TinyDPS[/url][/td][td]Another lightweight healing and damage metre.[/td][/tr]
[tr][td][url="http://www.wowinterface.com/downloads/info13357-AfterMath.html"]AfterMath[/url][/td][td]Calculates the damage your spells and abilities do after so many uses.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/honor-kill-tab-1-0"]Honor Kill Tab[/url][/td][td]Adds a tab under your PvP window to display how many HK's you have per BG total, as well as for the day. Replacement for Blizz's original tab.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/reflex-battleground-historian"]REFlex[/url][/td][td]Collects statistics of played BG's and Arenas. Includes wins/losses, with timestamp, as well as honor gained, damage/healing done, and deaths.[/td][/tr][/table]
[color=#ffa500][b]Other Utility and Miscellaneous[/b][/color]
[table][tr][td][url="http://www.curse.com/addons/wow/achscreenshotter2"]AchScreenshotter2[/url][/td][td]Automatically takes screenshots of BG final scores and whenever you get an Achievement.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/acp"]Addon Control Panel[/url][/td][td]Adds an AddOns Button to your main menu for fast in-game management and UI reload.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/altoholic"]Altoholic[/url][/td][td]View your other toon's bag/bank/equipped items, etc.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/atlasloot-enhanced"]AtlasLoot Enhanced[/url][/td][td]Shows you gear and where it is from.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/bagnon"]Bagnon[/url][/td][td]Better version of OneBag3 in my opinion, turns the normal backpack into all one bag.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/bejeweled"]Bejeweled[/url][/td][td]Best game ever.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/blizzmove"]BlizzMove[/url][/td][td]Easier version of MoveAnything, just less detailed.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/Chatter"]Chatter[/url][/td][td]Customize chat.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/hflootroll"]hfLootRoll[/url][/td][td]Neater version of standard need, greed and pass frames.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/Masque"]Masque[/url][/td][td]Pretty buttons for less clutter. For example with [url="http://www.curse.com/addons/wow/buttonfacade_elegance"]Elegance[/url][/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/move-anything"]MoveAnything[/url][/td][td]Allows you to move WoW UI and change the scale of the item.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/onebag3"]OneBag3[/url][/td][td]As the name suggests it turns the normal backpack into all one bag.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/prat-3-0"]Prat 3.0[/url][/td][td]Customize chat.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/preform-av-enabler"]Preform AV Enabler[/url][/td][td]Lets you queue BGs with a raid group, if the other players have this this AddOn installed.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/safequeue"]SafeQueue[/url][/td][td]Queue Mod, tells you the time you have to enter a BG or Arena.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/tip-tac"]TipTac[/url][/td][td]Replacement Tooltip AddOn, I love it so much.[/td][/tr][/table]
[color=#008080][b]Stand-Alone UI Mods[/b][/color]
[table][tr][td][url="http://www.wowinterface.com/downloads/info19994-DuffedUIV5Continued.html"]Duffed UI[/url][/td][td]UI replacement, it's a modified Tukui v13.[/td][/tr]
[tr][td][url="http://www.curse.com/addons/wow/nui"]nUI[/url][/td][td]UI replacement.[/td][/tr]
[/table]
Feel free to suggest more AddOns to add to the list or remove from the list.
Thanks to Mehcritkillu, Hurrx, CIHC, Twinko, Yde and Fourtwennay.