I thought this was pretty cool, especially as someone who is waiting on the PC version, I hope it isn't seen as spam.
Basically they are asking for $150,000 to create Squigly as DLC, and will release her for free to everyone on all platforms for 3 months should it get funded. It's already 1/3 of the way there at the time of this posting. They have stretch goals for other characters as well.
They even break down the costs of everything so you know what your money is going towards, which is pretty neat.
More importantly, contributing at least $30 will get you a pre-order/beta access of the Steam version of the game, and an exclusive TF2 hat only available through this campaign. There are more rewards past that tier, but this was the one that stood out to me personally.
I hope this succeeds, I think it's neat that DLC can get crowd funded like this, instead of putting it out on someone else's dime and then being in a tough spot should there not be enough interest or something.