Spider-man loves... Silver Sable?
Someone asked about this (although it wasn't a Request per se)
Since it's an old comic I can post 7 scans, right?
Okay, What-if v. 2 #21, it was a part of a special "Marriage issue" in two parts ("What if Spider-Man had not married Mary-Jane" and "What if Spider-Man had married the Black Cat") The way I heard this (which might be apocryphal) was that the first part was actually an alternative they kept around for pretty long before it was finally decided that Spidey and MJ actually *would* get married. (apparently there is a lot of rather interesting back-room politicking in that decision, and it's at least partially to blame for Felicia seemingly getting a lobotomy and a personality transplant)
So, in the previous What-if issue MJ is attacked by a supervillain and Spidey breaks up with her "to protect her", he then spends a lot of time fighting crime with Silver Sable, before at some point giving Felicia a call, the last page of the last issue is Felicia doing the "You hit the Jackpot!" scene. Heh.
Well, in this issue they get married, in disguise (Peter wears a pornstasche!) Felicia's still not comfortable with Peter Parker, but as long as they're fighting crime things seem okay.
Only Felicia gets sloppy and accidentally reveals Spidey's secret identity, it eventually finds it's way to Spider-man's deadliest enemy... THE VULTURE!
So he attacks Aunt May, Spidey finds out that Cat was sloppy and dumps her. He considers talking to MJ about the entire thing, but instead has a chat with Silver.
God Silver has a creepy smile.
So they go off to chase Vulture. Only he ends up killed any people blame Spidey, which ends in a big stand-off with the Wild Pack (which includes Sandman and Paladin at this point). MJ shows up to vouch for Spidey's innocence and gets caught in the crossfire, but then Felicia swoops her up because... To be honest I have no idea, she's clearly jealous, but also confesses to killing Vulture. The Wild Pack figures Cat took a hostage, which kind of confuses Felicia.
Only MJ slips from the ledge she's standing on (on "residual particulate matter from Sandman" according to the caption, lol) which brings us up to the end.
So in typical What-If fashion half the cast dies. Felicia is still written as a psychotic loon in this what-if (and not the clever master-planning cat-burglar she was in her first few appearances) and it's mostly notable for the rather left-field pairing there at the end.