I just started playing Bayonetta yesterday, I had it for a year but I never really tried it. So far I really enjoy it, reminds me a lot of Devil May Cry (which is also a good one) The story is ridiculous and the characters are the worst but it lends itself to the whole 'over-the-top-spectacle' that these games love to play up.
Devil May Cry 4 - Good game, pretty repetitive especially if you are doing multiple runs. They pull a MGS2 and make you play the first half of the game as a different character though.
Bayonetta - Underrated, solid so far even if the characters are insane. Camera is also pretty lame until you adjust it.
Dante's Inferno - Pretty decent, although much easier than the other games in my opinion. I just felt awkward if someone was watching me play since every 5 minutes there are boobs in your face. I really liked the setting, Hell was well built.
Ninja Gaiden 2 - Ugh, the camera is the worst for this game which only adds to the difficulty. If you can see past that it's a good game with some solid combo's. just don't say I didn't warn you.
EDIT: also if you meant 'hack-and-slash' as in more of a diablo style game check out Torchlight on the XBLA