I vote third party, because the first and second parties are terrible and don't in any meaningful way represent me, and regardless of the winner makes little substantive difference.
I also consider my vote to be a near complete waste. I am under no illusion that it really matters. Our system is massively supportive of the two-party stranglehold and a sub-10% vote is never going to sway that one bit.
But I can sleep at night a little better knowing that there isn't a single joke of a politician in Washington pulling a paycheck with my vote attached to them and that is worth a little bit I guess.