I tend to keep quite a few fish that are considered fairly common on this site but a few that I've yet to try and would like to raise one day would be:
Green Terror
Convict pair
Red Severum
Tire track eel
Fire eel
Group of Clown loaches
Just to name a few "common" fish; common being a fairly loosely interpreted word on this site
Dwarf puffers, bichirs, clown loaches as well as different species of botia - don't have the room for more tanks atm. Have owned Oscars and would love to have one again but definitely don't have the room.