A Lovely Bloom
One of the few conventional shaders that still functions as expected, this one looks really nice, and the screenshot doesn't really do it justice. It gives light sources a nice bloomy glow that softens things up a bit.
HDRTV
This shader saturates colors somewhat and adds faint scanlines. It has been around for a long time (it was one of the original shaders available for bsnes when it first got pixel shader support) but the scanlines weren't visible on 2D sources, so I was surprised to see them here.
NV+MSAA
This shader uses the "natural vision" algorithm to do some color adjustment with added post-proc anti-aliasing.
Cartoon
This one darkens the image too much to be very useful in an already dark game like Quake but may be good for future cores that have brighter games.
Edge Detection
While not necessarily practical, this shader draws a line at each color intersection to produce a cool, old-timey effect.
One of the only scale/interpolation shaders that has any noticeable effect, this one is a bit blurry for my tastes but it evens out a lot of the jaggies.
Scanline3x
I'm a sucker for scanlines and these normally crummy-looking scanline filters I made a while back actually look pretty nice here. (Note: I think I got the 3x and 4x mixed up; 3x should have fewer, larger scanlines than 4x)
Scanline4x
Themaister Waterpaint Scanlines
While the effect isn't as pronounced as with 2D cores, this shader does some smoothing with scanlines and ends up with a sort of screen-door effect that nevertheless looks pretty good.
Some of the bsnes-style CPU filters work, but not that well. The NTSC variants all perform their normal functions, but the the image is off-center and cuts some things off, as pictured. The scanline filters work pretty well, too, though they're sort of hard to see. Interpolation filters like HQ2X seem to have no visible effect, and SuperEagle crashed my game :/