against a good opponent i would normally always try to go all in with AK (shoving over a 3bet or shoving over a standard raise when you are oop) because you get called very often by AQ or AJ. especially at the beginning of the match when they think you're just messing around...
if your opponent has negative ROI, i would do this also with AQ, because you're get called by Ax very often. ace rag included.