That is a pretty open-ended question considering the multitude of small fish available.
I prefer region specific so here's a couple;
Indonesia:
x2 Amphiprion clarkii, Clark's clownfish
x4 Sphaeramia nematoptera, Pajama cardinal
x2 Ecsenius stigmatura, Tail spot blenny
x1 Nemateleotris decora, Purple firefish
Atlantic:
x4 Serranus tortugarum, Chalk bass
[SIZE=-1]x2 Apogon maculatus[/SIZE], Flame cardinalfish[SIZE=-1]
x1 Centropyge argi, Cherub angelfish or Centropyge [/SIZE]aurantonotus, Flameback angelfish
x1 Opistognathus aurifrons, Yellowhead jawfish or Opistognathus rosenblatti, Blue spot jawfish