The Bi-color Blenny has personality and is an algae eater(soft algae on rock) but sometimes likes green star polyps or acropora if it can't get enough algae.
The Rainfordii Goby is an algae eater and a pleasant tankmate.
The various Naso Tangs like macroalgae and sometimes like Valonia/Bubble Algae.
The Lionfish is an amazing sight, and is reef safe but I recommend the dwarf lion. The Volitan just grows and grows eventally eating any fish large enough to fit in it's mouth and stupid enough to go to sleep! There is an unlimited supply of live Lionfish food at Sea Base, but can be taught to take brine and other prepared foods.
The Squirrelfish is interesting and has large eyes, because it is nocturnal in nature.
The Royal Gramma is cute, though a meat eater, and has interesting habits like building a macroalgae nest and hanging upside down under ledges. My 10 year old daughter named our first one "Flower".
Bangaii Cardinal are very peaceful tankmates though again another carnivore.
Perhaps one of my favorite herbivore/omnivores are the dwarf angels. Flame Angels can clean an algae covered item in a day where snails and hermits can't reach it or Tangs don't want it. Coral Beauty Angels are prone to "ich" but if you like the look, one of these angels is definitely the fish to get.
Well, there are more but that should give you a start!