I've always had a soft spot for the
Fokker D.XXI
They were outdated from the start, but the Finns were sure glad to have them.
Another favorite is the often overlooked
Dewoitine D.520.
Nice picks. I actually completely forgot about the D.XXI in this thread, even though it's one of my favourites too.
The D.520, though, is just sublime. I'm a little more partial to the MS.406/410, but the D.520 is fantastic.
If any warbird folks here aren't much into building models but wouldn't mind a few nice birds, I can vouch for the Easy Model 1/72 pre-builts. It's a goodish selection in a lot of interesting markings and decent quality.
I'm not sure I'd pay @$20 full retail for them, but there's a couple of Chinese sellers on eBay who sell them for less and that's where I go to get them in batches. They might be factory seconds, since a few have some small flaws, but you have to look hard for the errors. I haven't bought a full price one, so I'm not sure if these flaws are present in the full price versions.
I've bought about 30 so far, and the only one with a major issue was an Aleutian Tiger P-40e that, for some reason, was missing markings on one side.
ETA: Also, as you might expect, the models are the "swastika deleted" variety. This includes the Finnish-marked aircraft, where the swastikas are either broken lines or replaced by big blue squares.