I like oranges. They really blow up when they're hit. Any kind of fruit. Potatoes work great too. Plus, they're biodegradable, so you don't have to clean them up if you don't want to. If you have even the slightest welding talent(unlike me), reactive steel targets are real easy to fabricate. At my USPSA club, we've got a setup with 2 rows of 6 each round steel targets set behind each other. When they all fall, a guy standing behind you pulls a cord and resets them all at once. I'd love to have one of those for my personal use.
I've only got two hands, but I've been known to carry three Glocks.