A few of us on here must to travel frequently for work - what are the things that annoy you about hotels?

I'll start ....

The Fridge: -

Make sure it is bewilderingly noisy, after all it's in a bedroom. 

Preferably, the socket should be located somewhere difficult to reach.  That way guests will try and push through the noise and get to sleep.

Optimally the fridge should be empty except for single serves of UHT milk, which don't need to be refrigerated. 

If this isn't possible, the fridge should be full of overpriced minibar items, so there is no room for the customers own purchases from the reasonably priced liquor store next door.