You can do what other land owners try pulling on churchs. They find their land is contaminated, and they know that it will cost thousands to clean it up. The DNR will find out about the contamination , if they try to sell the property, so they try to sign ownership over to the church. They almost managed this at least two times at one church in about three years time span I know of.
Never get a beta version of anything, it always costs you more money, and is a pain in the butt.
A Volvo. Preferably a “turbo” model.
A parrot, with no cage or accessories or anything. It’s like raising a child.
Get their teenager a drum kit. Get their younger child an intro violin lesson.
One way airline tickets to Las Vegas.
You can always donate money in their name to a charitable cause they despise. That’d be pretty funny because they’d be on the mailing list after that.
In the end its probably best to not be passive aggressive though. But this is fun.
Unwanted pets just hurt the pets, it’s not worth it.
My wife was recently given a sample of some type of make up sold only at Macy’s. She loved it so it was off to the mall to get some more. The smallest bottle was $89. It’s back to the drug store brand for her.
It’s even better than raising a child, because the parrot never grows up! I mean, it gets older, but it’s not like it’s gonna go off to kindergarten, and it’s never gonna start picking up after itself or be less selfish or anything - it’s giving somebody a permanent six year old. A really loud one.
A real top end imported sports car, like a Jaguar or a Porsche.
Then chuckle when they pay the insurance bills. Or take it to get serviced.
An ink jet printer. Keeping the thing in cartridges will be a real drain on the wallet.
A Polaroid camera.
(and please, like kanicbird said - do not give a pet to anyone for Christmas.)
Lots of great suggestions! I’m really leaning towards the ‘tickets to a special event’ – they live way out in western Ma, so anything in Boston ought to do it. Even if they end up not springing for the hotel room, the gas for the drive should be evil enough. 
Though I’m also torn by the idea of the new printer. Not just an ink jet, but a PHOTO printer. Don’t some of those use six to eight colors of ink? And, no doubt, you must toss a cartridge as soon as any shade runs dry. And they need special, very expensive paper, too, right? What a great gift!
(No, I won’t buy anyone an animal, I promise.)
Yup. I just read somewhere the other day (Demand a cite at your peril!) that paper and ink for photo printers ends up being considerably more expensive than having your digital pictures printed by a film processor.
Which I guess makes sense, because they have the economies of scale going for them. If you get a photo printer, it’s because you want the convenience of printing things off when the whim strikes.
Make suer it’s a Dell or Lexmark printer. They use the most ink and their cartridges are the most expensive.
If they don’t already have one of those freakin’ huge dictionaries, get them a stand for one.
A Scientology personality test, and the dianetics book.
Any impractical kitchen-clutter accessory like a “Mr. Beer” fermenter, a machine for making shaved-ice treats (which typically come with a small starter set of ingredients for margaritas or cherry icees or whatever, a mini-Bundt cake set (all those ceramic pieces to store, and they don’t nest inside each other, either), or a fondue set.
I was checking out an ad for the fermenter, a $30 (or was it $40?) starter kit. It comes with a starter package of ingredients, enough to make about 20 beers, and then you have to buy more beer-ingredients packs (and you get those where? Mail order, perhaps?). It isn’t cheap, either, setting you back as much as just stocking up at the liquor store. A bonus, for you pass-agg gifters: beer-fermenting is a tricky business. I once lived in an apartment where a previous occupant had had a beer explosion; the stains were still on the walls and ceiling. (I ended up doing some painting.) And after all the work, risk of mishaps, the unpleasant smell (it does smell, doesn’t it?) in your home, and the expense, the beer is probably extremely mediocre.
I say go with a “Mr. Beer” – the gift of those who just want to say, “suck on this!”. 
We have a Winner! Please select your prize from the 2nd shelf.
You can always do the most terrible and sign them up for a bunch of free trials for magazines. But that’s just mean.
Wrangle them an invitation to a ball or special dinner. There’s the cost of renting or buying tuxes and gowns, transportation, having to sit through stuffy dinner conversation, and the kicker–donations! Bonus points if you score invites for a Presidential ball for your leftist friends, or a DNC fundraiser for conservos.
Or how about one of those booklets of movie tickets? Most people like popcorn and pop when they go to the movies; that’s at least an extra ten dollars.
As a former owner of a Lexmark, I know their cartridges ran $30-35 (unless you got them on sale). And if one of the wells in the color cartridge ran out before the others, then what you printed wouldn’t look right until the cartridge was replaced. Unbelievably frustrating and a real money drain.