Noise ... especially when I have to get to bed early or sleep in due to my report time. It's bad enough from the other guests but loud banter from the maids (or them knocking on my door) is something they should be aware of as part of good customer service training.

By the way, I started using a 'white noise' (background noise) machine app on my phone on my layovers and it seems to help cut down with being awakened by noises. There are several available but I use "White Noise Free" (TMSOFT) and I like it. It's available for both iPhone and Android.