If you like beer and cycling, this is the tool for you: a spanner with a bottle opener at the other end.
The handy Beer Wrench by American bicycle company Budnitz attaches to the bolts on a bike frame where the water bottle would normally go.
Here's a picture of one of their bikes:
And here's a bit of info from Budnitz:
Our lovely Beer Wrench has a titanium 15mm spanner on one side, and a bottle opener on the other. Two titanium thumb-screws attach it securely to the water bottle mounts on most bicycles (including ours).
The 15mm wrench will remove rear axle bolts, Alfine internal hub bolts, and Pitlock keys, making it perfect for removing a wheel on the road. The bottle opener opens... a beer. Or a bottle of San Pellegrino. Or any other fizzy bottled beverage you might suddenly be in need of on an extended ride.
Engraved quote from 13th century Japanese Zen Master Dogen, helpfully reminding lost riders that we're always exactly where we're supposed to be.
Weight: a paltry 35 grams.