This one is easy.
I am thankful for my right to vote.
The ability to transition government without violence or forceful suppression is a beautiful thing, and one that is not currently a universal right. The ability to take part in that choice by voting - without coercion, without having to state what my vote is - is even rarer and as a woman, this right is one I wouldn't have had a hundred years ago.
While the right to vote exists in this country, there are those who will be experiencing intimidation as they go to exercise that right today... there will be people trying to discourage voting by targeting minorities or gays or other groups in neighborhoods unlikely to vote their way by selectively 'investigating' the validity of their registrations. That isn't to say that I don't favor valid voters... it is saying that such efforts aren't about weeding out invalid voters.. it's about making so hard to vote that some won't bother.
And there's a good reason to be opposed to that - because any tactic a group is willing to use to win can and will be used to ensure they lose at some other point.
I'm very thankful that we can vote - and I stand by that right for those who will vote my way, vote in opposition to my way, vote in ways I love or hate - because beyond all the issues of the day, our ability to take part in the process should make each one of us stand a little stronger in our own understanding of our responsibilities to our community, our country, and our world.
(That said... I must 'fess up and say that I am also very grateful that this is the last day I'll have to hear 'rubber-stamp-for-Obama' in the DUMBEST series of campaign ads I've ever seen.)