The Edge starting using the Digitech WH-1 Whammy pedal during the writing of 1991's Achtung Baby. If memory serve me correctly, it was Brian Eno that brought the pedal to The Edge's attention.

 

The Edge used/uses this effect during the intro of Achtung Baby's "Even Better Than The Real Thing", the Batman Forever soundtrack tune "Hold Me, Thrill Me, Kiss Me, Kill Me" and the "747" sound in the intro/transitions on "Gone" from 1997's Pop. The Whammy can also be heard on the Passenger: Original Soundtracks 1 album that U2 recorded with Brian Eno.

 

While the original WH-1 was only made for a short time and go for 500.00 plus in the used market. It has enjoyed popularity and resurgence thanks to The Edge and Tom Morello (Rage Against the Machine, Audioslave), both whom prefer the tone of the original 16 bit WH-1 to the 24 bit reissue.