My keezer holds 8 kegs. I always like to have one with an OG of 1.080 or bigger on tap. I currently have a tripel on tap that meets that spec, with a 1.092 quad secondarying in a glass carboy ready to take its place once I keg it.
Past kegged big beers have included wee heavy, RIS, and double IPA. I think if I ever brewed one again, I would probably bottle a barley wine, as the kegged big beers taste great but never get the aging benefits of bottled beer stored at cellar temperatures since they stay chilled at all times. Years ago I brewed a Fuller's Golden Pride clone/homage that really aged well in the bottle - I even remember mailing a bottle of it to Denny, as it seems he was questioning whether you could brew a decent barley wine with WY1968 yeast (I got 83% attenuation). That was a long time ago, I might be wrong.