40gal is a very nice sized tank. Are you going to want to convert this into a reef down the road?
Here are some fish to look into....
wrasses - sixline, eightline, fourline, yellow 'coris'
pseudochromis - fridmanii, springerii, strawberry, flavivertex, neon
grammas - Brazilian, royal, black cap
hawkfishes - longnose, flame, falco, spotted
chromis - green, blue, blue-green, purple
cardinalfish - pj, bangaii, flame
dwarf angels (further down the road) - flameback, coral beauty, flame, eibli
clowns - percs, clarkiis, marroon, tomato, cinnamon, saddleback, skunk, etc.
jawfish - yellowhead, dusky, tiger
gobies - sleepers, watchmans, prawns, etc.
blennies - bicolor, redlip, lawnmower, midas
I'm sure I left something off of the list, but all the fish I mentioned are pretty hardy for the most part. Some are a lot more aggressive than others. Do some research and chose wisely. Bo