Congo volcano ramp is pretty great. Similar to the right ramp in Road Show but it's tighter through the pops and has excellent theming.
I love all of J-pop's ramps. His signature flowing style is gorgeous to watch. He makes other designer's straight angled ramp returns seem so boring. Gomez has had some great flowing ramp moments — Monster Bash particularly.
Can't forget Nordman either. Scared Stiff's ramps are so satisfying to shoot, huge sweet spots, smooth entries and awesome flow around the ramps.
I find that great sound effects that compliment the visual movement of the ball can make a good ramp truly great.
I also agree with Doctor Who's O-ramp. I may not count because it is successive shots to this ramp that are particularly satisfying, not just one.