First under appreciated player that pops into your head

[Snowman]

Hitters:
It's gotta be Frank Robinson for me as well. He was an all-time great. He should be just one tier below Hank Aaron and Willie Mays, but he's usually an afterthought that gets placed several tiers too low. He gets no love. And since every thread needs a card, here's a Frank Robinson that I just won on eBay a few days ago

Pitchers:
Satchel Paige. Yes, he gets praise, but I believe he was the greatest pitcher who ever lived. He deserves more flowers.

Also, I find it interesting that some have stated Warren Spahn, as I believe he is the most overrated pitcher who ever lived. His stats were hyper-inflated by his ballparks (yes, so was Koufax, but not nearly to the extent that Spahn was). If you were to take all pitchers in MLB history and make adjustments to their numbers for park factors, Warren Spahn ranks as the #1 most helped-by-park pitcher in MLB history. That is to say that he would lose more WAR due to park adjustments than any other pitcher in history (depending on which WAR calculation you use, as some already bake this in). That said, Warren Spahn was indeed still one of the all-time greats. He just wasn't quite as great as everyone thinks he was.