Re: Ever been thoroughly underwhelmed by a pedal?
The secret to playing with flange and phase is to play to the peaks. You have to anticipate the point in the waveform you want to hit the notes, and how much swell and dive you want to be heard. Jake E. Lee used a flanger for solos and set it to an almost auto-wah sweep rate. Sustained bent notes were hit as the sweep reached its peak, so you got the "open wah" sound.
You can time your notes to get a "tone swell", similar to the solo to Megadeth's "Sweating Bullets", or to get a "oww" sound like the intro to U2's "Mysterious Ways".
For phaser, at least the BOSS Super phaser I had some years ago, you can fiddle with the settings to get a tremolo effect, or you can set it for those inverse "mewwww mewwww" Reggae sweeps, or a straight "jet flyover" sweep. I used mine mostly for tremolo effects, like the intro riffs to Alice Cooper's "Halo of Flies". Definitely works better for single-notes than full chords, at least in the forefront of a mix, but then that started life as a keyboard effect, according to the BOSS manual.
When paired with a pitch shifter/octave effect, you can really unlock a phaser's potential on guitar, like copping those swirling overdriven Hammond tones of Jon Lord without actually having a full-on Leslie and Hammond rig.
Put it after a delay pedal, set it for a sharp, fast tremolo effect, hit a chord and fill the delay's memory, then mute the strings and turn on the phaser. Machine Gun on the fly.
Someone mentioned not knowing how to use a delay earlier:
Like phase and flange, mostly you have to play to the effect, rather than work the effect into your playing. Delay can be used for "echo canyon" reverb far better than a reverb unit, especially a spring tank.
Or, it can be used as room reverb without coloring the tone like a spring tank does.
Then there's Rockabilly/Surf slapback.
Then there's the "classic" unity-volume repeats like the intro to Welcome to the Jungle.
Once you start getting into looping with one, things can get really interesting, as well as really messy in a hurry.