I don't vote. A small number of people give me crap about this. I'm philosophically opposed to democracy for a lot of complicated reasons. The mathematical reasons, however, are simpler and more universally compelling.
According to a paper by Andrew Gelman, Nate Silver, and Aaron Edlin, as a resident of a state that's strongly in favor of one candidate, I have a 1 in 60,000,000 chance of casting the deciding vote. That's 0.0000017%. The chance of winning the New Jersey Mega Millions jackpot is 1 in 18,500,000–about 4 times more likely–yet I never buy a ticket. My chance of dying in a car crash is 1 in 16,419–more thank 3,600 times more likely–yet I still drive daily.
Why waste my time? I make no other decisions based on such low probabilities.