Not quite a skyscraper, but an excellent cor-ten structure none the less:
John Deere Headquarters
Moline, IA
Eero Saarinen
harryallen.info
Can we talk about how awesome Cor-ten looks with bronze glass windows for a minute? I despise bronze windows with just about everything except black or cor-ten structural members. Time-Life in Chicago is one of my favorite buildings in the world because of this color combination. Also its white and turquoise and red and green neighbors add to it to create a delicious mash of color and texture.