Huldran
W:O:A Metalhead
Ragnarok,
Be prepared for chilly weather too - night times at Wacken 2005 were bloody freezing. Take a decent sleeping bag or you might freeze your nuts off.
I've invested in a quality sleeping bag for this year as I'm going to be in a tent this time. (was in a nice warm camper van last time).
Oh, and make sure you collect a full set of small Wacken beer mugs. I only collected 4 at Wacken '05. At the start I didn't realise that (a) you pay a 1 euro deposit on them and (b) they're a collector's item, so I didn't start collecting until too late.
And make sure you get one of those 1 litre monsters as well.
It might be a good idea to take one of those "wetsuit" beer can holders (don't know what you blokes call 'em, but they're called stubby holders here in Australia) so you keep your beers nice & cold - they don't appear to exist in Germany.
2005 was friggin' cold in general
My conclusion after 2006 (which, on the contrary, was fairly hot) was: tarp for the tent is a must - especially if you have a cheap-ass "extra lightweight" tent.
Sitting up and getting a cold dew shower in your face right after awakening is a funny experience.