Okay, so "dangerous" really isn't the right word, but now that I have your attention hear me out. If I ask you to name that one beer that has, shall we say, an unusually pronounced effect on you does one immediately come to mind?
For me, that beer is Cold Smoke Scotch Ale from Kettlehouse Brewing Co. in Missoula, MT. I have no idea why that might be, though I've heard the same from quite a few others (like 10). Friends in New England (that's you, 2Beer Guys and Seacoast Beverage Lab), tell me their equivalent is Golden Monkey Belgian-Style Ale from Victory Brewing Co. I've had a couple of pints of Golden Monkey and can see their point. At least with Golden Monkey, its rich smoothness packs 9.5% abv, giving a good indication of where the effect originates.
Cold Smoke, on the other hand sits at 6.5% abv, a fairly normal mid-range spot for craft beer. Still, it has some sneaky quality about it that stays hidden until you least expect it. Cold Smoke is crazy easy drinking, crazy smooth and crazy good. It is dark brown and malty with just a hint of smoky roast in the finish. With 11 ibus, there's just enough hop presence to keep it from getting sweet. Aromas are of light caramel and toffee. It's even available in 16 oz cans and won a bronze medal at the 2009 Great American Beer Festival. Let it warm up a bit to get the real flavors out of it.
What's your most dangerous beer?