This is fun. Having to change your approach based on your weapon every few seconds gives it almost a WarioWare kind of feeling, and the explosive barrels are a pretty clever weapon.
The weapons kinda lacked power, though. Sometimes I wasn't really sure if I was even damaging the enemies. And there wasn't really any feedback when taking damage either, so I kept dying without realizing I was even low on health. These things are pretty easily excused in a game jam though.
With more weapons and maps, multiplayer, and art that wasn't put together in under 48 hours, I could see this mechanic making for a fun party game.