I recently kegged a 9.7% abv Belgian Tripel that was in a 10 gallon Rye Whiskey barrel for 2 months (which was almost too long). It came out really nice. I used my barrel rinser to rinse out some of the Whiskey flavor before transferring the beer into the barrel. The oak, Belgian esters, Pilsner malt and noble hops really blended well. The reaction people have when they smell it initially, without being told it's barrel aged is priceless. It's hard to stop drinking it.
Fermenting: Brown IPA, JeanBeer, Barrel Fermented Dreg Lambic, Brett Trois Helles, Carrot Blossom Cedar Mead
Drinking: RIS, Coffee RIS, Jalapeno RIS, Heavy Hopper v2, Dusseldorf Altbier v5, Oktoberfest v5, Dopplebock v2, Cider, Rye Berliner Weisse, Sauerkraut Fermented Gose, Lambic, Brett Trois IPA, Brett Blonde, Kriek, Saison, Sour Blonde, RIS
Barrel aged: RIS, Rye Barleywine, Tripel, Wee-Heavy