Yonkyo is definitely high on my list, because my freakish flexiblity that takes the pain away from most other techniques offers absolutely no help with this one. And though I can't feel nikkyo from most nage, I can certainly feel it from my sensei, and he just loves to lay into me on this one
--payback for all the times he couldn't pin me I guess.
Last week, I got to be his uke for when he was teaching a bunch of newbies nikkyo. Lucky me. The nice thing about it was that I didn't even get time between each application to let my wrist rest a little bit. It was just OW! Drop. Up. OW! Drop. Up. Damn I love this stuff!