In my opinion, the big bad daddy of all cross-over beers is Great Divide Yeti Imperial Stout. Yeti combines some of the most intense roasted malt character you'll ever find in a beer with possibly the most intense hoppiness you'll ever find in a stout.
I perceive a little confusion over the classification of this beer. Traditionally, all stouts higher than 7% ABV were considered "Russian imperial stouts" (RIS for short). The name derives not from their origin, but their destination. Imperial stouts were first brewed in England in the 18th century to send to Peter the Great in Russia. A higher-than-normal alcohol content was necessary to keep the beer from spoiling on the long journey.
But about 20 years ago, along came the American craft brewing revolution and all the creative style-bending they brought to the world of beer. Whereas imperial stouts had traditionally differed from smaller stouts only in alcohol content (with perhaps a few extra hops thrown in to balance out the extra malt), Americans starting throwing in stuff like coffee, chocolate, heaps of citrusy American-grown hops, and sometimes aging them in bourbon barrels.
The Beer Judge Certification Program (the official governing body of sanctioned homebrew competitions) has simply adopted a definition of RIS that encompasses the diversity of modern American versions of the style. I think that muddies understanding of what was historically a very specific style of beer. The website BeerAdvocate.com has taken the approach I prefer by recognizing a separate category for American imperial stouts.
Oddly, though, BeerAdvocate classifies Yeti as a RIS, not an American imperial stout. I think that's mistaken because Yeti explodes with citrusy American hops. No traditional English-brewed RIS would have done anything of the sort.
Yeti coats your tongue with a ridiculous amount of malt sugar and hop oil, but the alcohol cleans your taste buds off very quickly. So there's a constant battle in your mouth as flavors of chocolate, coffee, caramel, dark fruit, citrus, and pine go to war. The result might leave you exhausted, but it will be a very contented state of exhaustion.
For the perfect pairing, put thus with dark chocolate. No wine in the world could come close matching it here. It would also go well with a hefty rib eye off the grill.