I'd love to find me a Siganus doliatus some day .. better yet, a pair.
A golden dwarf moray would fit in my 20g just fine
Any of the photosynthetic gorgonians.
Gorgonia ventilana or
Gorgonia flabellum. I know I'm dreaming.. it's too bad because they are supposed to do really well under conditions that are ideal for SPS (high flow, high light). Someone on RC had one, they were in Quebec, they never replied to any of my PM's though. Not sure if that's a hint about how legally collected it may have been.
But there are several other species of photosynthetic gorgonians that are available from some of the larger US based vendors (pacificeastaquaculture.com, liveaquaria.com, a couple others), but for some reason they just don't seem to come available up here nowadays (I'm guessing more due to lack of interest or people just don't realize that there are such things as photosynthetic gorg's that don't need a drip system for feeding!)