I mean, money is the obvious answer.

It's telling that the first thing that popped into my head was 'A lifetime supply of well-written fanfic for all of my OTPs.' It's more telling that after thinking about it for several minutes, That's probably still my answer, if money is off the table.

I don't actually drive, but free gasoline whenever I needed it would be a good one. I'd probably drive if gas was free.