So, to head off the age-old argument of "what makes a technique 'aikido'" (which would be a great different thread, by the way (ahem)), I'll say that I've seen many, many techniques done by aikido shihan who trained under the founder that people might say, "Huh? I didn't know aikido had ------?" These techniques include sweeps, kicks, punches, sutemi, leg traps, pressure points, and so on.
My intention in starting this thread was to discuss which techniques were considered "paramount" by people here. I know many people who believe that ikkyo is the "most important." I believe Shioda sensei thought that shihonage included all of the most important principles in aikido. And so on.
Now, back to your regular scheduled programming.