Floyd Rose
Floyd Rose is the inventor of the "locking tremolo" (vibrato) system, or "whammy bar", for the electric guitar that bears his name. The name has become synonymous with this type of whammy bar, though several manufacturers make similar systems, Floyd Rose owns the patent on the design.
The system combines a lock behind the neck bridge (the "nut") of the guitar, which prevents the tuning ("machine") heads from being used and holds the strings taut, with a "floating bridge". The locking system helps to keep the strings in tune while the strings are slackened to a degree which wasn't possible with older "tremolo" systems, such as those found on Fender's Stratocaster, allowing "dive bombs", i.e. rapid lowering of the pitch of a note. Since the tuning heads are inaccessible with the nut in place, the Floyd Rose bridge has heads for fine tuning; the guitar is tuned before the lock is put on, then fine tuned afterwards.
The floating bridge also allowed the pitch of the note to be pulled up, something previous systems could not allow. This allowed guitarists to use extraordinarily wide ranges in vibratos, and also allowed the creation of new sounds. This comes at a price, however, as the bridge causes difficulty when played regularly: moving the guitar can cause the bridge to move, changing the tuning; heavy palm muting moves the bridge; and restringing the guitar takes longer.
The use of the "Floyd Rose" was popularised and endorsed by Eddie Van Halen. Many modern electric guitar players (Joe Satriani, Steve Vai, etc.) make heavy use of this and excessively use the whammy bar to generate new sounds that were not practical to achieve with traditional (vintage) tremolo systems, while most thrash metal lead guitarists made heavy use of the bar merely to create unsettling sounds: Slayer's "Raining Blood" (Reign in Blood) features a solo consisting entirely of whammy bar noises.
Though the use of the whammy bar waned in the 1990s, as it was heavily connected with hair metal, many guitarists have continued to use these systems to create new sounds; Dimebag Darrell, formerly of Pantera, made use of the bar to access natural harmonics not otherwise available; while Tom Morello of Rage Against the Machine and Audioslave uses the whammy bar in conjunction of the whammy pedal and pickup toggle switch to create sounds reminiscent of hip hop.
Digitech's Whammy Pedal is an indirect descendant of the Floyd Rose whammy bar; when the Floyd Rose came into popularity, several keyboard manufacturers added a pitch control wheel to their keyboards. Since this pitch wheel allowed more control over the pitch of a note than was posible with a whammy bar, it was inevitable that someone would in turn apply this technology back to the guitar.