I'd be Kagura because she looks like a brawler, and I'd so go around beating the crap out of people.
Azumanga people I'd beat the crap out of:
1) Yukari, because she's mean, and frankly, she deserves payback for that tray beatdown she did on Tomo.
2) Tomo, because she's annoying, but it'd be a gentle beatdown instead of a hospitalization. I mean, I like her after all.
3) Chiyo.
4) Kaorin, for being a neurotic whiner.
5) Chiyo chi chi, for being a creepy egotist.