Cascade
But I usually use it in combination with Magnum for bittering, Centennial and often Amarillo for flavour/aroma.
Have used Cascade all the way through in an Epic clone attempt but didn't like the 'harsh' bitterness, I much prefer magnum for the heavy lifting. I am currently trying to bring my APA hop flavour back a little from the citrus/grapefruit arena towards something less sharp, more ...hmmm... if it were music I'd be trying to turn down the treble and bump up the bass...any suggestions?
Simcoe? Willamette?