It's a long time ago but when I turned 21 we hired out a function room in a pub and invited close family and friends. We had a menu of pub grub that people could order a meal off that list. We provided some jugs of beer & softdrink & some caraffes of wine to start with then after they went people had to purchase their own drinks.

To be honest I can't remember what I was given for my 21st so it can't be anything memorable....but it was a long time ago.