Chuck and Sarah - Chuck
After failing to disarm what they think is a bomb, Sarah kisses Chuck before they die. But then...they don't. Awkward, yet beautiful.
Karolina and Nico - Marvel's Runaways
Their parents could very possibly destroy the world at any moment, and neither Karolina or Nico are sure of what they're about to face. Karolina kisses Nico before it all goes down, just in case she doesn't get another chance.
Eleanor and Chidi - The Good Place
Chidi and Eleanor's kiss literally helped Eleanor remember who she was and stopped Janet's void from collapsing in on itself. They were technically already dead at this point, but it still counts right?
Hook and Emma - Once Upon a Time
Does this actually count as a kiss? Regardless, a spell was cast on Hook's lips, and if Emma ever kissed him she would lose her magic. But when Hook was dying Emma gave up her powers and gave him mouth to mouth save his life. This one might be a stretch, but it's too good not to include.
Clary and Jace - Shadowhunters
There was only one way everyone was getting out of the Seelie Court alive, and it involved a makeout session between Jace and Clary. With magical vines wrapping around both Simon and Jace's neck, the queen told Clary the only thing that would save them was "the kiss she most desired." When kissing Simon, her boyfriend at the time didn't work, she was forced to face her true feelings to save them both.
Damon and Elena - The Vampire Diaries
While Damon lies on his death bed, he uses his final moments to tell Elena that he loves her. Wanting to make him happy before he inevitably dies, Elena gives him a goodbye kiss. But Katherine saves the day at the last minute, and Damon ends up surviving.