Who are tough non-HOF signatures?

[Bkrum]

I am preparing to tackle my long forgotten collection of autographs that I accumulated primarily via mail in the late 70s-early 80s. Most are on cards although there are some 3x5, cuts, 8x10s, etc. I also purchased some collections in that era so there is really a wide collection of stuff. HOF players are fairly easy to track but who are some of the more collectible, rare, non-HOF players from the post war era? Is there a website, price guide, collector forum, etc that I could dive into to learn more?
Also I'm surprised to learn it seems there is a market for "vintage" autographs with a standard ballpoint pen as opposed to the more modern Sharpies. And autographed baseball cards are less frowned upon that they used to be. Interesting stuff

[MrSeven]

Roger Maris signed quite a few items but his autograph is still IMHO a tad pricey for high quality examples.

[packs]

Curt Flood can be tough to find on a card.

I've always had a hard time tracking down a reasonably prices Waitkus on a card too.

[1963Topps Set]

Don't forget Thurman Munson, Ken Hubbs, Harry Agganis, Howard Fox, Minnie Rojas, Miguel Fuentes, etc...

[mr2686]

I'll throw in some harder ones for those that collect certain teams:
Diomedes Olivo - 1960 Pirates
Jim Umbricht - 1960 Pirates
Duke Maas - 1961 Yankees
Randy Bobb - 1969 Cubs
Gonzalo Marquez - 1972 A's

[Republicaninmass]

If they were done through the mail in the late 70s, you can kind of eliminate names who died in the 60s!