Ventured into the Mini Adventure server tonight. Good fun server and worth a look if you fancy something different.
Quick word of warning: to work it appears to modify your unnamedsoldier.cfg file so you might want to back it up before you play as I think it leaves the settings in place and you might get accused of cheating with some of them.
Basically, you play in the third person view which takes some getting used to. The twist, though, is that you have to find a 'doll' and when you press the use key near the doll, you shrink. This means that there are lots of little people running around the server and the odd giant too. You can hide behind boxes and bigger objects, makes it quite interesting. It's not perfect, you can't jump through tiny gaps even though you should fit and because the cross hairs are the same height as normal you can shoot over and around the objects you're hiding behind. That adds to the fun though.
Worth checking out, but do remember to backup your config first.