(This is only in reference to nondecapitated skullfucking, because surviving your head being ripped off your shoulders is a chore in itself that makes surviving a skullfucking seem trite.)
I was thinking possibly Hank Pym at full Goliath size? If a "regular" sized penis punctured his eye ball, it wouldn't be hardly any more invasive than lite eye surgery.
Oh, and Shadowcat of course.
You'd have to have superhuman strength to fuck your way through/into the current of Cyclops Optic blast.
I know I said "and still have 20/20 vision" but you have to take note that Nick Fury's empty ocular cavity is not only preprepared for a good skull fucking, but it's probably not even empty and has traps in it to catch any penis off guard stupid enough to think it can get away with Skull fucking Nick Fury.
Is there such a thing as an astral penis to skull fuck Stephen Strange's third eye?
The Lizard (Wolverine earlier covers anyone with a healing factor, but the Lizards healing factor is like Deadpool times 11.).
Dead Girl? (She used to date Doctor Strange for a While.)
So you're about to skull fuck a still living Jamie Madrox the Multiple Man, and at the point of penetration (pun intended) when his powers do multiply him, it usually multiplies the clothes he is wearing, his wallet and on one occasion that I saw, also a gun he had in his pocket... So if most of your penis is inside Jamie Madrox's skull at the point of his death and it triggers one last knee jerk multiplication of himself... Is the dupe "fine" or do you yourself, being so intimately connected to Madrox at the moment of division (Odd no? Division and multiplication is the same thing here.) also become multiplied which has a knock on effect of creating a million, million, million new versions of you connected genitally to Madrox's face, or are there questions of mass, that his powers can't make another entirely new you every time they're triggered and so it's just a million, million, million dying Madrox Corpses synced up to what appears to be a million, million, million familiar severed penises?
The Swarm, is a swarm of bees who are haunted and possessed by the ghost of a NAZI scientist clinging to his unburied Skeleton. How many beestings to the penis can someone usually take before they pass out? So maybe if the Bees were sleeping, but they probably sleep in shifts, and does the NAZI Ghost sleep? If he did sleep, wouldn't the the bees just fly away? Maybe the bees like pretending they're people? But Like churning butter, odds are that you are going to turn a lot of innocent bees into a fine paste with your dick before you pass out from bee venom toxicity. It doesn't sound "worth it" but you have to remember that this guy was, and still is a NAZI.