I had an emergency C-section and had to send my poor dad out to buy some granny pants to cover my scar! Even if you have a normal delivery, the last thing you want is teeny tiny knickers.
They were not the most glamorous items, but they were certainly the most useful!
I would highly recommend a drink with a straw. This way your birthing partner can hold the drink for you during labour, which makes it so much easier!
My essential would definitely be hair ties. I ended up using an elastic band and it tangled my hair and hurt to get out. Never making that mistake again.
On the off chance that your baby sleeps that first night, I can guarantee that someone else's won't!