I've seen sloe, persimmon and kumquat made into lovely fruiting bonsai; there are a few stunning examples on this site, from a show: http://bonsaitonight.com/2011/12/27/enjoying-a-bonsai-show/

My garden is full shade, so I am not working with any fruit bearers; just the maples so far, which love it here. I put in the redwoods this month and just got an oak sapling that I'm going to try and shape a little bit. It's fun!