I love my red devils because they are little tanks... But they would out grow your 10G in about 6 -7 months, and thats if you get them when they're about an inch long and still haven't gotten their colour... That, and you can only really keep one once they mature cause they'll start killing anything they can catch...

I've always been a fan of neon tetras because they're little, fast and they tend to school... Plus, they look neato under a black light.