Taxa that I have really, really wanted to see for a very long time but either haven't (most of them), or I haven't been able to take a good look at. Since some of the traits, behaviors, or biology that I'm interested in are not taxon-specific (they'd make a polyphyletic group), some of them are just stand-ins for a particular thing I want to see. For example, Omphalotus olearius is a stand-in for bioluminescent fungi.

I've seen a couple of them and have gotten a good look, but I want to keep/raise/breed them myself, or I just want to see them again.