- Bring toe slippers - often there is a public road/path between the shower and your bed. It's the only way to keep your feet clean!
- Bring toilet paper in your hand luggage even on the first day. Many people get some form of stomach problems at some point along the way, and it strikes when you don't expect it!
- Bring lots of plastic bags to keep clean from dirty separate in your backpack. But don't litter, so bring them back home after use!
- Sun cream. Good sun cream is very hard to get in Nepal, and not for sale at all on the hiking routes. And the sun is dangerous up there, especially when you get to higher altitudes.
- Hand sanitiser. I normally never use this, but found it nice on the trek as it's often the only way to clean your hands.
- Woolly hat and gloves for the cold weather up high. Before you start your trek you're in the tropics, but when you get up high it gets very cold.
- Bring a torch. Some villages/lodges have no light during the night, which means pitch black toilets too.
- Knee bandage(s). I didn't bring these and regret it. Especially descending is hard on the knees and many people (including me) had knee problems. Good bandages can do wonders here.
- Most guesthouses have charging facilities except for the ones really high up.
- Mostly the charging points are limited, in some cases 1 or 2 sockets for the whole lodge. I brought a USB charger with 4 outlets which was often helpful to other people too.
- A backup battery device can be handy, especially a high-capacity one that can charge your phone multiple times. However, they often take something like 8 hours to charge, so once it's empty you're unlikely to be able to recharge it during the hike. Note that you often only get a few hours of electricity up the mountain, typically from 7pm - 10pm or so and maybe a few hours during the day...
- Wifi is often marked as available but outside the cities it's flaky at best. If you need to stay in touch with home you could consider a Nepalese simcard instead. They are pretty cheap, something like USD 2.
- Camera batteries don't like the cold high up. Bring a spare and keep camera and battery warm in your pocket.
- I'm not completely sure yet what the standard Nepali power plug is, but my European 2-pin plug worked everywhere.
- I would not bring water bladders again. They are messy to fill and can leak. Simple reclosable water bottles work better IMHO.
- Expensive 'hiking' socks - I had both cheap tennis socks as well as some 'proper' hiking socks with me. However I didn't notice the difference.
Disclaimer - this list is not exhaustive. Use common sense to bring what's important for you. This post is just an addition other lists about this topic available.