(zombies are pretty useful bunch).
Don't even get me started on zombies!
Seriously though one thing that has happened recently a few times is my jo feels totally alien. I can tell my jo from any other simply by touching/picking it up. At least three times in the last 4 months when I picked it up it just did not feel right and I could not do any techniques/kata without fumbling. The next day no problem.
I has been very unsettling to have something so familiar feel so completely 'wrong'.