Yeah the Aventinus Eisbock is fantastic. It's everything I like about Aventinus, concentrated into a potion. I like most eisbocks actually. I do prefer regular Aventinus though, it's more drinkable. Eisbock is, as you mentioned, one of those dessert beers that you chill with at night. For that, it's great though.
I heard that Eisbock was accidentally invented by drunken German brewers inadvertently leaving barrels out in the cold overnight.
Old Foghorn is a good one too. Tonight I had an Avery Brewing 'Karma' Belgian Pale Ale at dinner (I gave it 3 out of 5 on beer advocate, not the best).
But for dessert I'm having North Coast Old Stock Ale, a wonderful big beer. I hear it should be aged, but I can't keep them around long enough.
I did manage to age my homebrewed Barleywine for a year though. It's great, English-style, very syrupy and malty. I named it Bummelei Barleywine, and brewed it in Dec 2013. Should be good for another year or so.