GMforPowergamers
Legend
There was a warlord ability you could take that (I think it was daily) was epic... an ally within Xft/sq gets hit by an attack... immediate interrupt, you move to next to them, then swap places with them, you take the hit, then get to make an attack (I don't remember damage but I am sure it had to be at least 3w) then if the ally is in range they can make an attack...See, I'm OK with these. Because you ate still just fundamentally hitting someone, with a bonus attached.
It's when we get into the actual magical things, I consider a Gish/Magus as the first choice.
there was a much lower (maybe 3rd level) encounter power called "vengeance is mine" and it was an immediate reaction to being hit by an attack. you or an ally could make an attack back with a bonus to damage.
there was a fighter power (I want to say 5th or 7th) called 'sunder armor' where you hit you deal 2w then the target loses 2 off there AC until the end of the encounter.
there was a fighter at will 'tide of iron' where you push a target 5ft, then move 5ft to be adjacent and get an attack.
those are all combat though... but atleast it was options... like you could choose to do things.