Oooh, lovely thread, though it's probably going to lead to a lot of Advent Calendar Envy on my part! I'm torn between horror that massively overpriced calendars for adults even EXIST, and the desire to have multiple ones on the go. 
So. I'm a bit of a scringy Grinch about this. Years ago, after having been a bit disappointed with DS1's Star Wars calendar (a few minifigures, most of them 'festive' so no good for general play, and a lot of fairly lame lego miniature models) I decided to put one together for him. I made a fabric calendar and raided ebay for new and 2nd hand exciting lego bits and pieces - things he actually wanted.
The thing has cost, every year, easily twice what the commercial Lego calendar costs. 
But it's nice. Today he got a 'Republic Trooper' which apparently was spot-on.
DS2 has autism and doesn't get the whole concept of one-door-at-a-time but I'm making him a fabric one (hey, only five days late so far) and will put a maximum of three days' worth of chocolate coins in at any one time.
Me? Last year, after being publicly sniffy and privately covetous about adult calendars, I bought myself a really nice tea calendar (I think it was German) which was a real treat - loads of different loose leaf teas. It cost about £35 and this year I thought mm, maybe I can persuade DH to use the carcass of the calendar and buy some teas to go inside. He did this but unfortunately only about five different varieties, and they're all (apparently) black teas (I prefer green) so I'm a tiny bit disappointed but he did actually take the hint. Today my tea was salted caramel.
DH has a homemade Pinterest Fail special 
with 24 Hotel Chocolat chocolates wrapped in gold foil hanging off some twiggy shite, and three miniatures of whisky to be opened as needed. I didn't ask him which chocolate he chose this morning, but I note that we're now one bottle of whisky down... (and trusting that was last night, not first thing today)