Leopard bushfish (ctenompoma acutirostre) you can keep these in a group but make sure they're added at the same time as they can be territorial, quite a few catfish but my choice would be synodontis nigriventris (at least 6 since they like groups), african butterfly fish (pantodon buchholzi).
Smaller spiny eels like the peacock eel (macrognathus siamensis), striped peacock eel (macrognathus aculeatus), indian striped peacock eel (macrognathus aral), half-banded/zig-zag eel macrognathus circumcinctus. If getting these you may want to take a pic or something with you of one you know it properly IDed to make sure the one at your LFS is correct. They are easily mislabeled.
Most of the upper jaw bichirs: Palmas palmas, palmas buettikoferi, palmas polli, delhezi, senegal, retropinnis
Smaller knifefish like african brown (xenomystus nigri) or brown ghost knife (apteronotus leptorhynchus)
That's all I can think of off the top of my head, unfortunately I don't know a bunch about oddballs. Be sure to have sand for the bichirs and eels and I would not put the bichirs with the african butterfly fish as they are very likely to get nipped. And ofcourse make sure to do plenty of research on each of these, Seriouslyfish is usually a good resource and of course always feel free to post questions about them on here
