My favourite boost...
Everyone's got their favourite pedal that they kick in when your all the way up, all the way up, and need to go to eleven. What do you use for that "extra little push over the cliff"?
My favourite is an octave fuzz.
I have a few really nice heavy Rectifier patches on my GT-6, which are awesome for rhythm work and chunky chords. But on one of them, i've got it set up to kick in an Octave Fuzz and some delay when i hit the "CTL" footswitch. The sound is completely over the top and totally unique. I get a really wild square-wave sound (almost like an analog organ) with some pretty wild high-frequency overtones. It screams. It howls. Stomp on the wah, and it gets even more crazy.