9. Darth Maul's Return - Star Wars: The Clone Wars
Darth Maul made a brief but memorable appearance in The Phantom Menace, and his fight with Obi-Wan in the finale became an iconic scene for the series. He was eventually cut in half, which is a fairly failsafe way to ensure someone is dead, but Star Wars wasn’t going to let a detail like that prevent them bringing back him back.
It turns out being bisected wasn’t a huge deal for Maul, since the heat of the lightsaber cauterised his wound instantly, and he was able to break his fall by catching a vent on the way down. This was revealed in Star Wars: The Clone Wars, where he made his comeback, teaming up with his brother and intent on seeking revenge against Obi-Wan and causing all sorts of hassle.
Lucas has approved of his return, and Maul's gone on to appear in expanded universe comics and Star Wars Rebels. Who knows, he may even emerge in a future movie.