I'm going to go with a Mr. Aqua 12g long.
Plants will be a Christmas or flame moss wall, and a complete carpet of dwarf baby tears (for a few months, then who knows).
The only thing that has stopped me from purchasing it is finding the right lighting. I've gone through many 12g long threads, but nothing is conclusive. And if I could save $50 buying a less popular light that is just as good, that would be great.