As soon as I get a (real) job I'm buying two things - a tremelo pedal for my guitar and a Digitech Whammy pedal.
The tremolo pedal, for those of you that don't play guitar, gives the tone a repeatingly wavy, sharp, shaky tone, think surf guitar. Cost:$80.
The Whammy pedal, $200, not to be confused with a wah-wah pedal (Hendrix - "Voodoo Child") might produce the craziest sounds I have ever heard. It cheats for you. Jack White's solos that seem to go higher in pitch than our ears were meant to hear ("Ball and biscuit")? Whammy pedal. Weird heavy metal shit that alternates between a train screeching on the tracks and all over the map sonic shifting? Whammy pedal. I'll never, ever be able to play like this guy in the video, or even describe what I do as playing the same instrument as this righteous ass hole, but I still want the pedal.
Side note: it doesn't just shift the tone sky high, you can use it to make your guitar as deep as a bass, ala the first low notes in "The Hardest Button to Button." Also, I've basically just written an Ad for Digitech, I need to trick some people into reading this blogg and convince Digitech to give me a free Whammy.