I used nano-reef alot when I had my 10g running. The guys there spent alot of time putting together a great fish guide that was especially for nanos.
http://www.nano-reef.com/forums/index.php?showtopic=74703&hl=fish+guide">http://www.nano-reef.com/forums/index.php?showtopic=74703&hl=fish+guide</a>
It recommends 1-2 of the following:
-Yellow Assessor
-Blue Assessor
-Chalk Bass
-Lantern Bass
-Bicolor Blenny
-Tailspot Blenny
-Yellowtail Fang Blenny (V)
-Threadfin Cardinalfish
-Three Spot Damsel
-Talbot’s Damsel
-Three Stripe Damsel
-Firefish Goby
-Helfrich’s Firefish [$$$$!]
-Purple Firefish Goby
-Bicolor Psuedochromis
-Diadem Pseudochromis
-Fridmani (Orchid) Pseudochromis
-Purple Pseudochromis
-Scooter Blenny [with caution, not for beginners]
-Red Scooter Blenny [with caution, not for beginners]
-Painted Frogfish
-Wartskin Frogfish
-Blackray Shrimp Goby
-Orange Stripe Goby
-Orangespotted Goby
-Randall’s Shrimp Goby
-Yasha Hasha Goby
-Wheeler’s Shrimp Goby
-Yellow Watchman Goby
-Rainfordi Goby
-Royal Gramma
-Falco Hawkfish
-Flame Hawkfish
-Pearly (Yellowhead) Jawfish
-Possum Wrasse
-Sixline Wrasse (note: some believe 20g+ may be more suitable, if you buy one for a 10g, get it small)
-Ocellaris Clownfish (False Percula) (1, if you want a pair, move up to 10g+)
-Percula Clownfish (True Percula) (1, if you want a pair, move up to 10g+)
-Green Chromis Damsel
-Yellowtail blue Damsel
-Blue Neon Goby
-Catalina Goby [cold water]
-Clown Gobies
-Eviota Gobies
-Panda (Clown) Goby
-Redhead Goby
-Trimma Goby
-Yellow Neon Goby
-Citron Goby
-Green Banded Goby
Hope it helps!