I would suggest a red wolf fish or shoal of exodons. Red wolves are pretty mean looking and are most active of the wolf fish. Nothing too complicated with them. You might be able to keep a couple other fish of similar size with a red wolf, just depends on yours.
I have seen shoal of exodons (sabertooth tetra, a name you may like ) videos and they are pretty fun to watch.
that would be a payara. i think you have your teeth confused.
the colloquial terms most commonly used for exodon paradoxus would be bucktooth or sawtooth tetras.
but its best to stick with "exodon's" so save yourself from the confusion.
I second the Elong!! The black masked is really sick! Only grow to about 6 inches incredibly aggressive and they don't have the typical piranha shape. Second fave characin next to Armati.