Hitting radiator with fingers and scrapping over with a metallic object (car-key). Additionally amplified, notch-filter and accented subs. Results in a interesting sound scape. I've started to save my files in pcm format (instead of acm) because there was additionally quality loss. Recorded with a ultra cheap microphone unit of my mp3 player. Reduced noise.
Five strikes with a steel hammer on a 100 year old, 200+ lbs blacksmiths anvil. Recorded with and akg c2000b, presonus digimax fs mic pre to an alesis hd24 digital recorder.