My 75g is mostly doradids which do nothing but look awesome and spiky and come out to eat when the lights go low, but I have a pair of what have so far been the most rewarding catfish I've ever owned, the hoplosternum littorale.
But my 55g is all movement all the time. Between a satanoperca leucistica, a giant blue betta, a pair of silver mollies, an albino CAE, a gold dust bichir, a brachyrhamdia meesi, an adult zebra angelfish and a baby adonis (I'm forgetting somebody, I'm sure) there's always something amazing going on in there. Takes extra water changes but the plants keep the water crystal clear and everyone gets along oddly well. I am super happy with my 55g.