I bought bony fish canopeners keyrings for every single key set we own. If I'm not inside my house, I have a bottle opener. Hydration is important!In the crowd I dive with...
A bottle opener.
(after dive of course)
I also recommend putting a few regulator 1st stage o-rings (those ones you most often need) in your wallet. You might not always have all you dive gear and all your backups (training at the pool for instance), but you almost always have your wallet nearby.