Yes those generous types over at Studio Eres are currently allowing people to pay whatever the heck they like for Immortal Defense, their glowy tower defense masterpiece.
They're currently trying the pricing model out so there's no specific time limit or such but they also reserve the right to stop doing this at any point - so go check it out now while you have the chance!
For more info on the game, well you could check out my review (which I seem to remember was dubbed as fairly dull by the creator of the game...But he did offer some invaluable suggestions afterwards!) over here.
And of course there's this YouTube vid:
Don't forget there's a free demo, just incase you were still unsure about paying $1.75 (minimum amount you can pay) for an awesome tower defense game(!)