Greatest Time-Travel Duels Of All Time(lines)

Some of the greatest battles in science fiction haven't involved dogfights or shoot-outs, but time-traveling smackdowns, with two different people trying to change history out from under each other. Like Marty and Biff, trying to wipe out each other's timelines in this clip from Back To The Future 2. As soon as you have more than one time machine, you can have timeline-altering sniper fights, and whoever can erase the other person's time line first wins. Start your paradox engines, and may the slipperiest time-trickster win!