Is this going to be your first SW
tank? If it is, I would also strongly suggest at least a 10 gallon. SW
critters are typically much more sensative to water quality parameters and for the tank to be healthy the water parameters need to be stable. In a 1 gallon tank I would think it would require a fair deal of dicipline and experience.
If you have that experience and still want to go with a 1 gallon, then I would second QS's comments that really no fish would fit a 1 gallon system. I would say probably a few hermit or some snails and a little LR
. You can have many interesting life forms simply on a piece of LR