Loads of great lists on here, my favourite things I took are:
Eye mask for sleeping (lights are dimmed but never out)
Sports top bottle for pouring water over as you pee! Also those moist toilet wipes will come in very handy during the early weeks.
Arnica tablets - they are herbal so hospital won't provide them, but they can help ease bruising. I swear I healed much quicker than I expected after my episiotomy.
Nice toiletries - it might seem silly but after giving birth when you're living in hospital you feel a bit gross at a time when you deserve to feel special! I took some Sanctuary Spa minutures and now whenever I smell them it takes me back to watching my tiny new LO sleep in her plastic crib.
Similarly I got a set of matching nightie and robe plus new towels - all black (stains!) and all cheap Primarni but it just helped me feel nicer, especially when visitors showed up.
I also packed a bag of snacks and bits for my OH - it can be a long haul for them and you need them to be able to support you!
Energy drinks, cereal bars and also food they can make with just hot water like pot noodles or those porridge pots you can get (don't forget a spoon!)
Plus a toothbrush, fresh tshirt and comfy bottoms.
Book and a phone charger.
(Of course my OH forgot the bag and was starving 🙈)