Other: When I was little, Santa and Mom&Dad. Then as we got older, Santa branched out. Suddenly, we got presents from his wife, from the elves, from the reindeer.
Then it was strange relatives we'd only heard of through humorous stories. Then fictional characters.
Pretty soon, we were getting presents from each others' anthropomorphised cars, our pets, favorite childhood toys, and The Marlboro Man.
Now that we're all adults, it's a competition to see who can come up with the weirdest sender, or the best tie-in to the actual gift. I got Asimov's Guide to Shakespeare from "Toast" one year - because we'd taken a pic of Bacon with some bread and captioned it, "Alas! Poor Toast, I knew him well!"