I'll second spiny eels as being very cool fish. But I learned the hard way that tyre track eels (Mastacembalus armatus) will eat platies.
Other cool community tank oddballs: Hatchetfish, bizarre-looking, and very aggressive feeders. Mine go into a feeding frenzy when I squish some prawn in the tank. Halfbeaks, pike-like, breedable, nicely coloured. Glassfish, when kept in groups are very active and even a bit thuggish. Reedfish (Erpetoichthys calabaricus), shy, must be kept in groups, but safer with not-to-small fish than bichirs. South American puffer, in my experience safe with fast-moving tankmates like tetras and barbs. Badis badis, needs a very quiet tank, e.g. with dwarf barbs, neons, etc., but an amazing colour-change artist.
Cheers,
Neale