i agree with the suggestions of razzies (slower moving, completely unaggressive), otos (unobtrusive, algae-eating, and cute), and cories (very much in their own world at the bottom of the tank).
whiteclouds are another nice danio alternative.
two or three kuhli loaches would probably work just fine. yoyos might be okay too, but they have a more aggressive reputation than the kuhlis, and eventually get bigger than the confines of a 10 would allow in the long run, even though they are slow growers.
a cherry barb will be a good addition 50-70% of the time (although we have come across one sweetheart and one real a-hole version of the species). they do not share the schooling needs of their other barb cousins, so it's perfectly acceptable to keep just one in the tank.
snails and shrimp are supposedly good tank friends too, if they are big enough to avoid being eaten.