Travelling with a nice friend. It is(was) easy to spend like 10-30k a month by living in 5 star hotels, eating fine cousin, shopping etc. But travelling alone sucks.

Learning skills from actual world class experts. Including things one might not normally think of as a skill but might be influence-able from osmosis.

We're not as unique as we think, but we're not anywhere near as uniform as this question implies. At the very least, answers will vary based on timeframe, and on future spending expectations, and on past experiences of fun or surprising un-fun.

You might find it fun to give a random responder to a web forum question $50k. At least try it once to find out.

Alternately, and an interesting idea: http://www.overcomingbias.com/2020/04/what-can-money-buy-directly.html recommends hiring a happiness agent, who you pay proportionally to the happiness you actually gain.

What a fascinating question. As a self-proclaimed hedonist and an egoist, I feel compelled to throw in my two cents.

First of all, it's crucial not to spend this money recklessly. If you do, and you end up regretting this waste of money for significant time, the anguish will outweigh the fun. You are better off if you never had the money to begin with.

That means you need to know reasonably well what will bring you fun before you pay a lot for it. Significant portion of the 100k budget should be distributed over many smaller experiments that might bring you fun. If you expect to have similar fun budget in the future, perhaps even entire 100k should be spent that way. And even if you have clear idea of what brings you fun, it's still worth to drop a few k every now and then into new ventures, to see if they might increase your fun. This is quite tricky: things that at first seem to deliver a lot of fun might habituate easily, so repeated experiments might be in order.

I would also recommend that this budget is spent over some time rather than in a single shot. I know that in my pursuit of fun, more often than not the anticipation was more enjoyable than the thing itself. Also, when I knew that my purchase of fun was time-limited (e.g., it was a short trip), I was pressuring myself to make the most out of it and thus significantly diminishing the fun I was experiencing. I now make it a point to keep myself perpetually in a state of anticipation of near-future pursuits.

Now, some specific ways that may or may not bring you fun:

• Gifts for people you care about.
• Travel. Try doing it solo and with a friend, see what works better.
• Vanity: Getting professional haircut, grooming and style advice.
• Prostitution (if it's legal and not coerced in your area).
• Signalling wealth (expensive watch, jewellery).
• Prestige (get recognized for making a substantial donation to some org).
• Activism (you can get a lot more done in an NGO if you don't need to look for funding).
• Vengeance (no specific ideas here; I do like The Count of Monte Cristo, though).
• Home upgrade (easiest way: stay in a lot of AirBnBs, see what you like, be extremely picky based on those criteria when searching for future homes). <- This advice is HUGE and possibly the greatest contributor to my enjoyment of life.
• Professional equipment for any hobbies you have.
• Eliminating un-fun (get a maid, order food delivery instead of cooking, use Uber instead of public transit).
• Like-minded people (if you think that you would enjoy the company of LessWrongers, move to the Bay Area, perhaps only for a short period of time at first to try it).
• Time (quit your job, or at least get unpaid time off; or switch to working part-time).

It's time to go to bed here in Europe. I will probably add some more tomorrow.

Things that will improve your amount and quality of time spent with friends and family. Games to play together, vacations to go on, housing in close proximity or transportation costs, admittance to events. What has high marginal benefit depends strongly on your situation. I know one guy who had more money than friends, and moved to a town with his family and old friends, and then scaled up the blues dance scene in town (spending say a thousand dollars worth of food, another thousand or two in subsidized lessons, and plenty of time and expertise) and made new friends there. But this strategy wouldn't work at all for someone in a different situation.

Plausibly, things that will improve your attractiveness - nice clothes, healthier food, a few sessions with a personal trainer. Or if you think you've got the basics covered, maybe efficient signalling by buying fancy versions of inexpensive things.