Forgive me for getting overexcited, but my latest stamp lot contained two stamps with inverted overprints. I've been waiting to 'discover' stamps with inverted overprints for ages - and it's happened at last!
Unfortunately, this one doesn't have the complete overprint (well, it does sort of - but one letter is far over to the other side):

But, as if to make up for it, the other one has got two!

Honk if you love inverted overprints!