I originally had 5 guppies and 5 espei rasbora, and 3 died, and another was aggressive. So I was left with one guppy happy on his own. Most guppies prefer friends, though. So, 2 platies did the trick.
You could do something like this:
-4 Male Guppies
-2 Male Platies
You will almost certainly not find espei's rasbora, they are not common, and I got them by accident, they were labeled as harlequins and are smaller. If you have sand you could do a tank full of cory cats. :)
Livebearers like guppies and platies like hard water, and most tetras prefer soft.
Most barbs are nippy, and fight a lot. Cherry barbs are relitively peaceful, though. But I don't know if they fit in a 10 gallon.