Zildjian 20” Crash Of Doom was supposed to be a wild card cymbal and then somehow worked it’s way into my regular set-up. So dynamic and versatile for something folks think about as FX cymbal. Moody and dark but also has a beautiful wash that sits great in the mix for me - love it.
I love my 20" A Custom Crash, they have a certain darkness that the other sizes in that series just don't have. It's super thin but still projects well, not the loudest crash by any means though. I'm also a huge fan of the 20" K Crash/Ride and Sabian's 20" HHXtreme Crash for something a bit darker and trashier.
I'd second that, although I do wonder how the 20" thin would work. I have yet to try.
I'd add a Sabian Vault 20" V-Crash. It has a fairly mature sound with a bit of "zing" to it. Perhaps a good cross between the glassy nature of a Paiste and the more full-bodied sound of Sabians and Zildjians.