Inspired by the discussion  about Hincapie's stem in Paris-Roubaix: What are your "best" mechanical failures? Here are mine:

a) Stomping it over an overpass, broke a crank arm off. Yup. That sucked. Yup. Racked 'em. Brand: Stronglight.

b) Peugeot Super Vitus KOM: early attempt at a light, thin steel frame, before the metallurgy was all there. You know how those Pillsbury biscuits come in this cylinder that corkscrews open? Did that to my head tube climbing a hill.

c) Hey, is my front wheel always that far out front? Nope. Broken fork -- Marin Treviso.

d) 1987 Rock Hopper: that twisty feeling is the chainstay separating from the rear dropout.