Years ago I had a roommate who was a carpenter, and I copied a habit from him: Anytime he came into a little extra money, he’d use it to buy a specialty tool that he didn’t immediately have a need for, but anticipated he might someday. If you chose carefully, he explained, one day that tool would save your bacon. (Tools I can vouch for in this category are an air shim, a band clamp and a long, ratcheting Bahco driver with an articulating handle.)
The next tool I’d have to put in this category is this cool 10" Locking Adjustable Wrench by Crescent. It’s got the convenience of a vise-grip-style locking handle with a more hex-friendly jaw configuration: