I don't know if you'll have much luck finding something easy, but there are lots of reptiles that are cool!
I've always thought green anoles were pretty neat, and I'm fairly sure they would stay small enough for a 33 gallon. Some of my favorite lizards are bearded dragons, but I believe that they grow to large for that size of tank. Apart from reptiles, poison dart frogs are pretty neat, although from what I've read they might be a little tricky to take care of. Land hermit crabs (a kind of crustaceans, distantly related to shrimp) are pretty awesome too. (Here is my 55g land hermit crab tank, in case you're interested: 55g land hermit crab tank - 55 gallon Non-Aquatic fish tank
) Anyway, whatever you decide to get, just be sure to do plenty of research and post lots of pics!