You guys are gonna think I'm crazy perhaps, but I've been known to add +12-16 dB @ 20 kHz using Linear Phase Graphic EQ. I didn't set out to add that much, but a lot of my synth and drum machine patches sound really muffled. I keep messing with EQ until it sounds good, and sometimes it takes a lot of decibels. However, I don't use it on material which is already high-endy.
Usually when I'm doing that kind of crazy boosting, I start out at +24 dB, which sounds really bright and icy and slicy and sharp as needles. Then I bring it down until it just sounds clean and clear and not too harsh or shrill. I like to test it out on a variety of speakers though, because some speakers are more sensitive than others up there.
Like I said, a lot of my sounds are muffled. It's your classic turd polish!
