Mike & Ikes, Bouncy Balls, Gum balls, peanut m&ms, & skittles. Bouncy balls do great, however I had a location ask me to not restock the bouncy balls as they are a potentital choking / slip hazard.
I've had great luck with the u-turn machines. Three 4 head units, and one 8 head terminator. They're easy (& cheap) to fix, lots of parts available too. I managed to get every machine used for under $65.