I mentioned my late 70s guitar in another thread and it occured to me that that instrument had two of the absolutely iconic upgrades of the 1970s.

1. The Leo Quan Badass bridge. A combined tune-o-matic and stop tail made for Les Paul Juniors and Specials. The first of its kind and the start of "hot rod" parts. They're cast from zinc alloy these days but then they were just carved out of a solid lump of brass.

http://www.leoquan.com/html/guitardetails.html

2. The DiMarzio Super Distortion humbucker. The pickup that started the whole replacement pickup industry.

Without the success of these items, we'd have no GFS, no boutique pickup industry, etc.

So, what are your nominations for the gear that revolutionised guitar playing?