Here's a list of what I took.
Mobile phone (And I still got charged for using the phone in the room even though I never touched it. The nurses were using the phone! Got out of paying the bill for that thankfully)
Lip Balm (I found this essential as I ended up with dry lips)
3 Pairs of jim jams
Spare underwear
Going home clothes consisting of a pair of mega baggy pants to accommodate swollen and sore tummy
Shower gel, Shampoo, Conditioner, toothpaste, toothbrush, hair brush. Wet wipes. Talcum powder.
Moisturiser
Magazines. I had a lot of waiting around for my op and couldn't concentrate on reading but you might be different.
Slippers
All my current medications
I did take some Dry Mouth Spray as recommended on this forum but I didn't use it as I was taking sips of water after my op but others have found it very useful.
I think that's it, others will no doubt add other items if I've forgotten anything.