I think a bottomless bank account would be worth the trade.
But no devil worth its salt would take me up on it: if I could buy whatever I want whenever I want, my soul probably wouldn’t be worth all that much by the time I was done with it. 
Unlimited wishes, and no “monkey’s paw” funny stuff.
If I had a soul, i’d only sell it for something impossible. Like the powers of Q, for example.
Immortality
No, I didn’t say immorality, I’ve already got that.
I can’t sell my soul, it’s already got a lien on it. 
Oh, the poor sweetie. Now, there’s a mama for you. To hell with us, make our babies feel better.
I know she’s miserable, but it will pass. Let her chomp on your fingers as much as she wants.
That would do it for me.
On the other side of this topic, I own a soul. Some guy (early twenties, so it won’t be worthwhile for a bit of time) sold it to me for a cigarette.*
*At the time, I declined ownership. Enough time has passed to make me rethink that position, though, so I’m collecting. Heehee.
Be careful, Lucifer is father of all Lies.
Cue Twilight zone music
World peace achieved by all humans being wiped out.
Ooohhhhhhhh! I didn’t know I was selling it to Lucifer!
Still… maybe I shouldn’t trust the highest bidder on eBay. They might not pay up, either.
Came up around the lunch table once in High School… “If you had to make a deal with the Devil, what would you ask for in exchange for your immortal soul?” My buddy didn’t skip a beat, “His.”