Here's a few of mine ;]
Rogue:
#showtooltip Vanish
/cast [stealth, target=focus, mod:shift] Cheap Shot; [target=mouseover, mod:alt] Cheap Shot; Cheap Shot
/cast [nostealth] Stealth
/cast [nostealth, mod:alt, mod:ctrl] Every Man For Himself
/cast [modifier:ctrl] Vanish; Cheap Shot
#Showtooltip
/cast [mod:shift, target=focus, equipped:thrown] Throw; [mod:shift, target=focus] Shoot; [mod:alt, target=mouseover, equipped:thrown] Throw; [mod:alt, target=mouseover] Shoot; [equipped:thrown] Throw; Shoot;
/stopattack [mod]
#showtooltip Sap
/cast [nostealth] Stealth
/cleartarget
/targetenemy
/cast [mod:ctrl] Vanish; [target=focus, mod:shift] Sap; [target=mouseover, mod:alt] Sap; Sap
#showtooltip
/clearfocus [target=focus, dead]
/focus [mod:alt, target=mouseover, exists]
/cast [nomod,target=target] Gouge; [mod:alt,target=mouseover,exists] Gouge; [mod:shift,target=focus,exists] Gouge; Gouge
Druid:
I've got all of my Druid spells setup like this. In conjunction with /cast [target=Party1,2,3,4] Spells, I'm able to cast everything on up to 12 different targets without switching my current target
/cast [target=targettargettarget, mod:ctrlt, mod:shiftl, mod:alt] Rejuvenation; [target=focustarget, mod:shift, mod:ctrl] Rejuvenation; [target=targettarget, mod:ctrl, mod:alt] Rejuvenation; [target=focus, mod:shift] Rejuvenation; [target=mouseover, mod:alt] Rejuvenation; [target=player, mod:ctrl] Rejuvenation; Rejuvenation
/cast [target=targettargettarget, mod:ctrlt, mod:shiftl, mod:alt] Regrowth; [target=focustarget, mod:shift, mod:ctrl] Regrowth; [target=targettarget, mod:ctrl, mod:alt] Regrowth; [target=focus, mod:shift] Regrowth; [target=mouseover, mod:alt] Regrowth; [target=player, mod:ctrl] Regrowth; Regrowth etc
And the largest macro I use...
/cast [nostance, target=targettargettarget, mod:shift, mod:ctrl, mod:alt] Faerie Fire; [stance:3, stance:1, target=targettargettarget, mod:shift, mod:ctrl, mod:alt] Faerie Fire (Feral)(); [nostance, target=focustarget, mod:shift, mod:ctrl] Faerie Fire; [stance:1, target=focustarget, mod:shift, mod:ctrl] Faerie Fire (Feral)(); [stance:3, target=focustarget, mod:shift, mod:ctrl] Faerie Fire (Feral)(); [nostance, target=targettarget, mod:ctrl, mod:alt] Faerie Fire; [stance:1, target=targettarget, mod:ctrl, mod:alt] Faerie Fire (Feral)(); [stance:3, target=targettarget, mod:ctrl, mod:alt] Faerie Fire (Feral)(); [nostance, target=focus, mod:shift] Faerie Fire; [stance:1, target=focus, mod:shift] Faerie Fire (Feral)(); [stance:3, target=focus, mod:shift] Faerie Fire (Feral)(); [nostance, target=mouseover, mod:alt] Faerie Fire; [stance:1, target=mouseover, mod:alt] Faerie Fire (Feral)(); [stance:3, target=mouseover, mod:alt] Faerie Fire (Feral)(); [nostance] Faerie Fire; [stance:1] Faerie Fire (Feral)(); [stance:3] Faerie Fire (Feral)()
It exceeds the default macro size limit by almost four times, but I use the action bar addon Macaroon which allows for macros to be written with unlimited length