I travel to Berlin a lot to party. To answer your question about Kit Kat first: No, you likely wont find much piss action at Kit Kat. It is also mostly straight people doing the fucking, with the exception of some gay guys going at it. Kit Kat attracts a lot of straight people. The real Kit Kat though is also beneath Kit Kat. When you walk in, past the coat/phone check, youll see a little podium in the corner. Go talk to the girls there. Theyll ask you two questions: are you here with a girl? and if your answer is no, the next question will be, "are you gay?" And well, obviously youre fine. Then theyll put your name on the list and youll pay a small cover fee and descend downstairs into a cavern where there is a bar, a long tunnel where people are sniffing their keys, and then a large room where everyone is pretty much dancing naked. The large room where people are dancing has an upstairs area. On it are couches, again youll find mostly girls up there getting gangbanged. But you can also find some guys. Its just not the ideal place to go to if youre looking for sex (when youre gay anyways). On the other hand, if you like industrial techno and psytrance, Kit Kat is awesome. I usually go there on Mondays. Mondays the downstairs area will be closed, but the main areas of the club upstairs have great lounge areas, and then the dance floor. Above the dance floor are beds that people are fucking on.
Lab.Oratory is the raunchiest place youll pretty much ever go to. Youll find whatever you want to participate in going on there. Pay attention though to the theme of the night. Some nights are gummi nights, others are piss themed, others for fisting. I personally love the first fridays of the month when Lab doubles over as a sex/techno club. Its basically one large circuit party but turned up 10,000 notches.
Tresor is right next to Kit Kat and my personal favorite club, but its not really much of a sex club. Just great techno and trance.
Der Boiler is a wonderful bathhouse though. If youre specifically looking for piss, it ranks as just about any other bathhouse youll ever go to. But I love its dark room maze area with gloryholes, and it has a great lounge area for smoking outside. Its very nice there, clean, cool layout. Lots of men. They also pass out free lube packets at the bar so dont worry about having to bring your own.
Hope this helps.