Geos (except brasiliensis), guianacara, milder acara types, gold saum green terrors, angelfish, mesonauta, high bodied tetras, pink tail chalceus, lot of different plecos and catfish, arowana... some of the fish I've kept with severums. Wouldn't do salvini or pearlscale cichlids with sevs, too aggressive imo, as already mentioned.
...also various rainbowfish, pearl gouramis... probably others I'm forgetting....
Cool. What kinds of catfish have you kept with sevs?