Year It First Dropped: 2008

It's crazy when two fashion brands work together, let alone ones with such dedicated followings. Swedish Acne Studios teaming up with French fashion house Lanvin seemed totally random, but when lookbooks started to leak, it made a little more sense. Known for their denim, Acne put their "jeanius" together with Lanvin's designers, who turned out a subtly cool, indigo-inspired co-ed collection that contained everything from suiting to denim high-top sneakers. The collaboration was so successful they kept doing it until 2011.