I have a 120 and looking to stock it. I have a Leopard wrasse currently. I don't know if I want tangs that way I don't have to worry about them knocking corals over.
The fish you put in a tank is a pretty personal thing.
But here are some ideas.
Tangs - there are a few tangs that will live in a small tank like the kole tang or yellow tang.
Dwarf angels - these are reef with caution. The flame angel and coral beauties are popular.
Gobies - lots of gobies will do fine in that tank. Tend to be bottom dwellers.
Bennies - like gobies there is a wide assortment to choose from. Tend to be bottom dwellers.
Damsels - great looking fish but they can get incredibly aggressive. I understand that the talbots and yellow tail tend to be less aggressive.
Chromis - tend to be peaceful. People use them for schooling. They often kill each other off.
Anthias - like the chromis, a schooling fish. They are moderate in degree of difficulty and a bit more expensive.
Check out live aquaria. They sell a large variety of marine fish. They give a pretty good run down on each fish. It is a good place to do basic research for your wish list.
oh my, this is one wide open question for me. In terms of reef compatible, get a goby/pistol pair, one dwarf angel, two clowns, a midas blenny, and a flame hawk. As Marshall said, there are some really cool wrasses out there and I've really grown fond of them. They are so colorful and very active.