The kissers: Colossus and Rogue
Category: Kiss to gain power as part of X-Men strategy.
Issue: Uncanny X-Men #247
Set up: The X-Men were in a battle with Master Mold, who pounded Colossus into the ground. Colossus was shaken up and still in armored form as he tried to pull himself out of the ground.
The kiss: Rogue kissed Colossus, mouth to mouth with a gloved left hand on his cheek. In the panel with the kiss, Rogue explained, "Ain't got that kind'a time, sugar. Sorry 'bout this, but since you're in no shape t' use your power ... ah hope you won't mind me borrowin' it."
Colossus' face had turned to flesh, and Rogue's neck, lower jaw, and part of ear had turned to steel while her upper face was still flesh.
Result: Rogue absorbed Colossus and flew up in fully armored form.
Rogue said, "Someday, sweetie, ah just gotta find a way to smooch that don't instantly zap the guy I'm smoochin'!" Colossus was lying on the ground, out cold. After Rogue used the full speed hit from outer space tactic on Master Mold, we saw Colossus back in armored form and Rogue back to normal.