As in, you had the least expectation for, but actually turned out to be a keeper?
For me, it's an Agile Spalted LP, and a Peavey Foundation V bass.
Both were cheap as hell, but ended up being amazing.
The Peavey bass beat out the Fender equivelent (both MIA and MIM) Jazz Vs. It also beat out the other various basses I've had over the years. The only contender for me was a Warwick Corvette $$ 5....which was also fantastic, but I expected that.
The Agile was LP GAS induced. Even drove 1.5 hours to go to Dave's Guitar with the intention of buying/trading for a Gibson LP Traditional. They had at least 7 used ones, and 4 that appealed to me cosmetically. After spending a few hours dicking around with them, only one of 4 spoke to me. Sadly, it appeared to have a hump in the neck around the neck joint.

Ended up with an old PRS CE24 instead, which was pretty cool.
Anyway, a few weeks later I was watching eBay, and decided to take a chance on the Agile.
It showed up and was great, better than the Gibsons I had just played.
Don't know if whoever had it before me had set up work done on it, but it plays and sounds wonderful.
I assume it has the stock pickups, and I even like those.
What did you discover?