This image posted at Earth Science Picture of the Day would be hard to beat as the definitive angular unconformity. It shows Upper Carboniferous  marine metagreywackes folded during the Variscan orogeny overlain by Triassic redbeds. Structurally it is uncannily similar to Hutton‘s famous unconformity at Siccar Point on the coast of SE Scotland, although the tight folding there is Caledonian in age and the unconformable redbeds are Devonian in age.