If I was rich (I wouldn't want to be single).. I would build a modest size home, but it would have an indoor pool and one of those insane bathrooms with a big tub and one of those huge glass walk in showers with marble everywhere. Those are two things that I think would just be awesome. I also want 2 stoves, 2 ovens and 2 sinks in my kitchen, where I would learn how to really cook.
I'd take recreational pilot lessons and possibly buy a 2-seater small aircraft, hire someone to decorate my house right and have a completely finished garage and basement.
I would find a way to work 3 days a week somewhere, because I think that is the happy balance everyone needs, and it could be starting a business, and dumping obscene amounts of money into it the first year to make it the best even if it means never re-couping the cost later.