10. Mass Effect 2 - Death By Mind-Sex
The Mass Effect series is well known for its immersive world-building and complex character relationships - and let's face it, many of those relationships are memorable largely because of the "sexing your companions" element. The first game in the series caused a fair bit of controversy on release because of the sex scenes in the game, and that game doesn't even have Morinth in it.
In Mass Effect 2, whilst teaming up with Justicar Samara on her loyalty mission, you can replace her with her daughter, Morinth. It isn't possible to romance Samara, but that doesn't hold true for her daughter, who will gladly jump the Commander's bones.
The only problem is that Morinth suffers from a rare genetic defect which - given how the Asari mate by melding minds - kills their partner during sex.
Ignoring all common sense - and the fact that Morinth has killed every single sexual partner she's ever had - Shepard can accept the proposal. And, despite Morinth's suggestion that the Commander is different, having already died once, we're treated to a shot of Shepard's brain being fried, and then a Critical Mission Failure. Game over - back to your last save point as you wonder what else you expected.
Maybe next time you're propositioned by a psychic alien who's killed every partner she's ever had, you should say no. Just a thought.