Is there an addon like this?

I'm looking for something really simple, that perhaps could be bound to a key that would put a signal over the head of the next thing to be attacked when in melee combat. I get into that crowd, there's 25 people banging away on almost as large a crowd of bad guys and I lose track of what's what. I've looked at Curse and there's an array, but I didn't see something that seemed to be what I'm looking for.|||I just look at whatever my tank is tanking and click his/her targets panel (I use xperl for my unit frames).|||Or put /assist <name of tank or whoever you'd like to assist> also work, just put it in a macro and you'll target the target of your assist automatically!