You know what I love?
I love when the friendly people at my local Post Office use the round stamp and cancel stuff by hand if I ask them to. (It was one of the LetterMo achievement badges too!)
It's a good idea to do this if you have an envelope that could get damaged by the sorting machines, but sometimes I ask them to do it just because it looks way better and completes the work of art that the envelope was intended to be. It looks especially nice on the historic pieces, which I unfortunately don't have any photos of at the moment. I do have a photo of this piece that went to France, though...
And the ones that I receive are super cool too. Like this one from Budapest, Hungary:
Do you ever have your letters hand cancelled?