The 1954 Proof Roosevelt Dime DDO is a really neat variety that not many people know about even though it's incredibly easy to spot if you know what you're looking for. It can most easily be identified by looking at the 4 in the date. The 4 has a "blotch" that extends all the way down to the rim. The top of the 4 is also very noticeably different.
It's way out of my price range, but given that I was born in 1958 it'd be fun to own a 1958 DDO Lincoln. I only have one DDO Lincoln, and it's a 1972...
This is probably my second favorite variety. I got this from a nickel junk bin while looking for off date Hennings. I got it for $0.20.