I started to understand the "cave" part of "man cave" when, in our old apartment, my fiance would lower all the blinds to block out as much light as possible when watching TV. When we moved, we proactively darkened our TV room with a deep shade of blue paint.
After a few months of basically camping on the floor while waiting for a custom order that fell through (delivery guys couldn't angle it through the door - lesson in measurements learned!), we finally bought this Klyne sectional on sale from Crate & Barrel. It takes up almost the whole wall and gives us plenty of room to stretch out. The coffee table is a glass Craigslist find that we kept from our apartment.
We picked the wall color, Rain Storm by Behr, together. My fiance likes it because it adequately darkens the room, and I like it because it's basically my favorite color. The color is interesting and changes a lot depending on the light, and it also helps highlight the tray ceiling.
Images: Kim Rinehimer