The USPS almost lost my SO’s graduation present (a handmade, very nice black belt from a really awesome company in Japan that was also a celebration of his promotion to black belt) because they refused to deliver it to our mailbox (the package would have easily fit) and NEVER left a “missed you” notice. They “tried” to deliver the package twice, when everyone was at work, and didn’t check with our neighbors (very nice older couple, always there), and then put it in “lost mail.”
A month or two after ordering it, I finally call the post office with a tracking number, after translating the Japanese carrier service’s e-mails with the help of a friend who speaks Japanese. They won’t believe I have a tracking number because “it’s not one of ours!” NO DOY! I told you, the package was from Japan! It wouldn’t have a USPS tracking number, would it?
After two searches of their “lost mail” inventory (while I’m at work, with my boss watching me argue with them) they finally find it. But they won’t re-deliver it, even with my consent to JUST LEAVE IT IN THE MAILBOX IT FITS IN, or bring it to my neighbor. Thus, my mom was privileged enough to use her lunch hour to get the package, and apparently they took another hour searching for it with her because “that’s not one of our numbers.” They couldn’t even set it aside for her, after I told them she’d be coming to get it, because . . . they like searching for the same package over and over again, and arguing about whether Japan should use the same tracking numbers they do? Dunno.
That was 2 years ago, and it still makes me angry, because my SO didn’t get to wear the black belt I bought him until a few months after his promotion. I told everyone, “No, no, no, I’m buying him a really nice one from Japan, he doesn’t need one, save your money.” Like I said, still angry. That’s why I’m not a black belt yet, I guess 
Then there’s the time they refused to deliver my paychecks because I didn’t have the same last name as my (male) roommate . . .