I would hire a live-in personal assistant/housekeeper to do all the things I just don’t want to (laundry, cooking, cleaning).
(They would live in my new custom designed home complete with moat and drawbridge.)
Non-functional guns on a fortress are kinda like tits on a bull. When you build a fortress, you are announcing to the world “Here I am, and more importantly, here’s a bunch of my stuff you would probably like to steal.” When [del]I[/del] someone comes with a raiding party, you’ll be much happier with functional artillery.
I’d like to by my own Congress critter. Can I do that? Loretta Sanchez please. I’d go with pay off debts.
Yeah, but I can be more effective with one Ma Deuce .50 Cal MG than all the muzzle loading 24/48/96-pounders in the whole fortress.
Besides, the hidden claymores would be the real defence.
I’d buy crazy-shit jewelry. Like stones that have actual real names. And horses. (I’d buy horses, not buy diamonds that have horses.) And I wouldn’t hire a cook, I’d hire a busboy and dishwasher.
I don’t care what anyone else’s replies are - you have won the thread, hands down.
Well at least get a sous-chef; 'cause nobody likes to chop onions. . .
I’d buy a spellchecker. C’mon people! Nobody else is commenting on the title?! Frivious is a cool word in its own right! Aaaaargh pulls out hair
After I build my HUMONGOUS Home For Cats (free flea meds and spaying provided), like my very own SPCA only bigger - OK, OK, I’ll have a wing for dogs, too, but soundproofed!..after that…
I would have a truly decadent limo with mini-bar and super sound system, and driver available 24/7 to drive me EVERYWHERE. To the grocery store, to the mall, to McDonald’s, to the post office, to restaurants, to that antiques place out in the middle of nowhere, or just a ride for the heck of it on a boring Sunday. (My life might not change that much, I’d probably live like a regular boring person for a while.) Of course, Alfredo the driver would be available any time, day or night, blazing August or blizzardy February, to shuttle my friends and relatives around, too! “Alfredo, please take my mom for her umpteenth doctor checkup on Friday, pick up her prescriptions, and do her grocery shopping on the way home.” Oh, what heaven that would be! To never have to drive again!
I would be a space tourist. I would also like a burial plot in Pere Chaise. I am undecided over whether or not I would want to buy some original great art or provide very generous grants for talented living artists on the condition they produce a flattering painting or scuplture of me. If I went with that option I would also build a few wings on existing art museums so those paintings and scuplture could be displayed.
The ‘thing’ I would buy would be an almost endless journey round and round the world, seeing everything I want to see and trying everything I want to try, having great fun with carefully selected friends, and doing it all in great style and comfort. This would be paradise.
That’s what I’d do in my Tesla. 
I forgot about Vegas. I’d like to play in the World Series of Poker Main Event. I know I wouldn’t make it to the money, but it’d be so much fun losing it.
A big tiger sanctuary where they could do all their tiger things and I could watch them (safely)
“Hey, dawg, we put a limo in your limo because we heard you liked limos.” I think I could get on board with never driving again, especially if you were getting chaffeured around in such luxury that you would barely even have to register that you were on the road.
I’d by the Chrysler Dealership down the street and fill it with cars. Turn the back-lot into a Kart track, and leave 4 of the 8 vehicle lifts for whomever needs 'em.
I don’t know much about cars, what does this mean?
It’s absolutely not frivolous, but I would use my wealth for peace, goodwill towards men, and to build a 1984-era video arcade.
Asteroids
Dragon’s Lair
Defender
Q*bert
Qix
Donkey Kong (Jr)
Space Invaders
Crazy Climber
Moon Lander
Missle Command
That Atari Football game with the 6-pound trackball
(Ms) Pac Man
Gauntlet
and, of course…
Robotron: 2084
Peace, man.
ETA: Oh, yeah, I forgot. I’d buy some fuggin’ awesome weed. 
Lift…lifts a car off the ground. There’s two major kinds, a 4 post that you can drive on, or a 2 post that lifts from the sides so the wheels hang down.
The point would be to have a place, for free, where an enthusiat could do stuff to their car that would be difficult or impossible to do in their driveway.
Well, if houses count as frivolous, I want a hobbit hole.
With an indoor glass walled infinity pool.
And someone who design something like that, that works.