I'm with Dan. How do you narrow that field?
I really like the first 6 techniques of Purple Belt. I feel that, as a group, they are an excellent group to show the differences between the macro concepts of kenpo, jujitsu, and aikido, as well as an excellent place to introduce the 4 Phases of Kosho. Takedowns are introduced, though at this point, they are simply implied.
Aside from that, I really, REALLY like almost everything in 3rd black. It's as if someone said, "Now that you know a couple of hundred techniques, let's take 30 and refine them down to how to destroy somebody really really quickly, with very little effort or wasted motion, and look cool doing it."
Actually, I can. Don't like to, but I do it anyway.
I like the Arm Hook defensive move. It shows up in a lot of other techs, like Slashing Cougar, Waterfall, Sowing the Seeds, Leveling the Clounds. I sort of do it a bit differently, however, more like Wing Chun's Taun Sau. The angle is a bit different, but I think works a little better for me. This was one of the "ah-ha" moments I have had in studying other arts like Wing Chun, where a lightbulb went on in my head and something about my kenpo suddenly made sense to me in a different way than it did before.