Dropping a rig filled with Hydromorphone from shaky hands into the toilet has to be up there. And the... god damn microdot incident where I ended up losing about ~40 of them... outside... in the dark...
I was all benzo'd at home the other day and lost a baggie that had some baclofen and nifoxepam in it. I swear it's in my room somewhere, but I don't remember where I put it! >.<