I have a man cave in my home and it has the following:
1. 42" plasma TV
2. Xbox 360
3. PS3
4. All networking gear
5. Back-end server
6. Front-end HTPC
7. Main gaming system
8. Secondary gaming system
MOST importantly, however, is my Colts gear spread throughout the room -- one wall is painted Colts blue and has a Fathead Colts horseshoe on it. I've got some Colts stuff on the walls and some mini-helmets placed in the room too.
Another feature is "Corvette Row" -- I have die cast models of every Corvette generation on a hutch in the room.
I would also have had a beer fridge, but we have a full bar in our house and the beer fridge is there instead.