A minor-league player most of his career, Stubby Clapp did play for the Cardinals for a few games in '01. Love the guy, love the name - even if it does sound like a weird STD 
This one, I don’t get. The only connection between the two is the name. It would a great name though if Guerrero’s sport were fencing.
How about “Ock” Duliba (from the German song “Ach, du lieber Augustine”. I forget who he played for. I think he was better known for his nickname than anything else he did.
How about James “Cool Papa” Bell
A better name than Rays’ pitcher Grant Balfour.
Pity Rollie Fingers and Bill Hands were never on the same pitching staff. Bill Lamb, Bob Moose, and Stan Veale were, though.
I dig Mo Rivera’s other nickname, “The Hammer of God.”
Did he like Milli Vinilli?
Eric “Napalm” Gagne.
Not here to add any nicknames, but wanted to link the OP’s original suggestions to some pages with information about them:
Bob “Death to Flying Things” Ferguson
After that pitch of Randy Johnson (?) hit the bird flying by and killed it, I’d have thought that nickname should be applied to him! 
Maybe it isn’t baseball related…but i’ve never seen him naked, so who knows?
It’s hard to be Randy “Big Unit” Johnson.
Ah, yes … there was a time, very recently, when the Yankees’ rotation partly comprised “Big Unit” Johnson, Wang, … and Small. 
You reminded me of Bryan Clark, the so-called relief pitcher whose propensity to add to the flames of opposing rallies led him to be dubbed “Gas Can” during his stint with the Indians. The sobriquet played off Dennis Boyd’s nickname of “Oil Can” (mentioned earlier in the thread), which derived from a slang term for the beer cans from which Boyd apparently derived much liquid refreshment as far back as his teenage years.