I like the honey or dwarf gourami.... as the feature fish. some people have just one bit have read they do better more than one (male and female or 2 females in your size tank).
otos and pygmy Cory's are very cute and entertaining and will be your cleaners... the are schooling fish.
with gouramis you can have harlequins or cherry barbs (only small barns as bigger barbs can get nippy with gourami).
you could go down a. different route and have a betta for a feature fish (my personal favorite... I was going to stick my 20 gallon with gourami bit changes mind mind last minute...both I think are good choices). woth a betta the pygmy Cory's and Otos will be fine. and any peaceful fish, like harlequins, will be fine with a betta (unless you have an overly aggressive betta).
let us know what you decide