My immediate response to this was a little depressing, so I'm going with something fun instead:

The greatest torture for me, personally, would be trapped in an eternal groggy morning, forever getting to the coffee pot just after the last cup has been taken. Over and over, I'll set up a fresh pot to brew, only to find that it's always empty by the time I get to it. Absolute hell.

Alternately, you know those dreams where you really need to use the restroom, but you can't find a single working toilet? That.