Recover some stolen testicles. No, really.
The Witcher 3: Blood and Wine - Goodness, Gracious, Great Balls of Granite!
This quest can be found in Beauclair, the main capital of Toussaint - the massive city area. It's denoted by an exclamation mark as a point of interest on the map, and the NPC you have to talk to in order to kick this quest off is marked as an art curator. It can also be found on notice boards, which will direct you straight to the dealer. It's recommended for Level 36 and above, though it's almost all talking.
After hearing all about the crime at hand - somebody's stolen the testicles off a statue - use your Witcher senses on the crime scene. Examine the statue. Head down the short stairs just to the left, and you'll be able to find a torn rag. Its scent will lead you to the thief - so use your Witcher senses and follow that thief!
You'll be led to a house and meet the chap responsible for stealing the balls. The guy is involved in more than just ball-stealing, and is having it off with another guy's wife. Chat to them. The husband will then arrive, angry - you'll need to get rid of him, either by fist fighting him or by using Axii to mind-control him away. The latter is always better, as it nets you more experience.
After that, you choose what to do with the balls. You can let the guy keep them - which nets you a bunch of gold - or force him to give them back either immediately or in a few days' time.
If you retrieve the balls, the quest giver will give you the Reginald Figurine item after returning them to him. If you don't you'll still have to return to him to tie up the quest by lying about losing the trail of the thief.
If you give back the balls, you can return to the statue after a few days and take advantage of the curator's offer of free use of the relic, which is worth doing at least once.