Not a binocular, but probably my favorite accessory: the Stoney Point binocular rest. Much easier than using a tripod mount with a monopod, especially if you want to switch back and forth between bins.
Paid $16.95 for my first one.
Found these this morning, on clearance at $9.08.
I ordered two, and a couple of other items. 2hrs 10min later, I had confirmation that my stuff had already shipped.