Inheritance
Poor choice, you'll blow through it quickly if you don't earn it yourself.
Marriage
You think she keeps your balls in a jar now? Just imagine if she had all the money too.
Work
Work, while important, is not by itself a way to wealth. Particularly if you're a W2 employee on someone else's payroll.
Shiftily Pulling One Over On a Bunch of Rubes
One of the rubes will have a brother-in-law who is an attorney and they'll fleece you for everything you have for sport.
Gambling/Lottery
Craps is your best bet. Well-played you only lose about 50.5% of the time. Fun project: write an accurate craps simulation, run a few million trials, and see if you ever wind up with more money than you started with. After craps your odds really go in the crapter.
Stealing
Forfeiture laws. Heck, I'd turn you in for the reward.