I was thinking the same about a 6Gal I have sitting around. It would make a nice desktop accessory.
Fish options are VERY limited with a 2 gallon. MAYBE a clown goby, but i would prob just get some inverts, snails, sexy shrimp, emerald crabs. and some coral. Youll need to make sure you have lighting for coral if you want to go down that route.
People don't really do pico( really small) FOWLR because of how limited the fish selection is.