A night in Shinjuku

[chiquiliquis]

Alright all you enlightened party animals, here is the deal. A friend of mine is staying in Shinjuku for the next couple days. We are planning on hooking up tomorrow and going out for a little fun. I live out past Hachioji (west Tokyo) and have made it into Shinjuku a few times, but don't know the area all that well. So this is my question: if you were looking to have some fun in Shinjuku, what would you do, and where would you go--say, money was no issue... well, or say it was... either way, what would you do?

Is there any fun to be had in Shinjuku on a Sunday?

Plz note... I specifically mean Shinjuku... my friend can't get stranded in Shibuya/Roppongi etc. cause he's got business in the mornings.