This forum thread is full of great advice and tips for the Wrecking Ball achievement, in which you've got to get 20 killing blows without dying in a battleground. The key here seems to be to find a place with lots and lots of folks to kill (a spawn point, like the graveyard in WSG, works great, or you can hide behind the big groups in AV), and then just hanging out there as far out of the way as you can get. Having a pocket healer won't hurt either, and playing fair isn't really part of this one -- you want to duck in when you're sure to win the fight, and run like crazy when things even threaten to go against you.
Some people say that doing it at a lower bracket can help, too, because unless you're uber geared, it'll be better to go after lower levels than have everybody in the BG be 80. It actually sounds like it's easier than it seems -- as long as you set yourself up in the right place and be really careful about getting stuck in a fight you can't win, you should be able to walk away with the points. Good luck!