Anvilicious

Some full screen games make use of both the Alt and the Tab buttons. Accidentally press them both at the same time and...

... If you're extremely lucky, the game resumes when you Alt+Tab back. Usually, returning to the game ends up with the mouse still on the screen no matter what you do. Sometimes, the only way to close the now non-functioning game is to restart your computer.

All because you were holding down sprint while opening the menu.