6. Blindsighted 
I have picked this mission because it is one of only a few in the game to feature a cinematic cut scene, which I rather enjoyed. This is the penultimate mission in the Thieves Guild questline, and sees the Dragonborn betrayed by Mercer Frey, shot with a poison arrow by Karliah and then stabbed by Frey before being left for dead in a Nordic ruin. The camera blacks out as you fall unconscious, and it is then revealed that Karliah saved you and that the arrow wasn't poisoned after all, just designed to knock you out to fool Mercer. Smart.