Try a pike cichlid, bichirs, a Jack Dempsey would be good in a 75, or you could do a cichlid community which would be cool. If you were looking for a gar type, try to find a spotted pike characin, also known as a mosaic or Hujeta Gar. They arent true gars, but look and act like them. Really cool hunters, get about 10"-1'.
-LJ