Not an official source, but in one of my games there was a 5 day festival in a city that survived an attack by fire giants, ogres, and gnolls 10 years ago, and started a festival to celebrate their survival. In the lead up to the festival, people would decorate upside down barrels to resemble the head of the fire giantess who led the attack. The day before the festival began, a panel of judges would select the most fearsome head. The head would be attached to the top of a solid 30-foot-tall, 3-foot-diameter log.
The upper portion of this log would be decorated with heavy burlap stuffed with hay, and covered with a rigging of rope, forming a "torso." There would also be two 5-foot-long chains covered with thick padding, attached as "arms" and these could swing freely. The log would then be inserted into a 15-foot-deep shaft that was about 5 feet in diameter at the top, narrowing to about 3 feet in diameter at the bottom. Six 30-foot-long ropes radiated from the giantess's "neck." The ground surrounding the shaft is covered with 3 to 4 feet of hay for a 10-foot radius or so. A 10-foot-tall wooden platform is built just outside the radius, with an extendable platform that gets about 7 feet from the "torso."
Festival attendees can pay a silver piece to leap from the extended platform and grab hold of the torso's rigging. Once they have jumped, the platform is removed and a six-person team holding the ropes begins to rock the log back and forth in the shaft, and even spin it around, which causes the padded arms to flail about, possibly knocking the contestant off. I had a short table that I rolled on to determine what happened round to round, but it was basically a bunch of Strength checks and Dexterity checks at various penalties. Those who lasted 30 seconds (5 rounds) got their silver piece back. Those who lasted a minute or more got a gold piece. At the end of the festival the person who held on the longest was awarded 10 gold and was on the panel of judges for the following year, and the log and the barrel become the central portion of the great bonfire marking the festival's conclusion.
This is all done to recreate a heroic act witnessed in the assault on the city 10 years ago, where someone (no one knows exactly who...) leapt onto the giantess's back, stabbing at her while holding on despite all the giantess's attempts to brush them off.