WoW Macro Collection

Target Cursor Location (AOE)
/cast [@cursor]ABILITY_NAME

Target Cursor or current target (single)
#showtooltip
/cast [@mouseover][]ABILITY_NAME

Target Player Location (Personal buff)
/cast [@player]ABILITY_NAME

Player & Cursor Modifier
#showtooltip Sigil of Flame
/cast [mod:alt, @player][@cursor][]ABILITYNAME

Help/Harm Mouseover Target Macro
#showtooltip
/cast [@mouseover,nodead,exists,harm][nodead,harm] HARM_ABILITY_NAME; [@mouseover,nodead,exists][help][]HELP_ABILITY_NAME

Swap Ability automatically (When Switching Talents/Build)
#showtooltip
/cast [talent:5/1,@mouseover,harm,nodead,exists][talent:5/1]ABILITYNAME1 ; [talent:5/2,@mouseover,harm,nodead,exists][talent:5/2]ABILITYNAME2 ; [talent:5/3,@mouseover,harm,exists,nodead][talent:5/3]ABILITYNAME3

Personal Favourite: Hides/shows the second Vertical Action bar:
/click InterfaceOptionsActionBarsPanelRightTwo

Combat Resurrection (Example)
#showtooltip
/cast [@mouseover,help,dead][dead,help]Resurrection