Small yellow watchman
Neon Goby
Clown Goby
pistol shrimp
Sexy shrimp
pom pom crab
(Temporarily!!!!!!!!) a very small ocellaris or percula. (would need to upgrade eventually)
The people who are saying no to fish in such a small tank are more or less right, you should provide a larger space if possible, but if using the proper amount of rock work, the above fish would do fine.
Stay away from any mandarins, the mandarins would be an okay size but they only eat copepods and would deplete a system that small very fast.
Also, I would suggest bumping up to the Fluval Evo 13.5, you can fit a better amount of coral and fish, and can run a protein skimmer, does better on evaporation than the 5 gal