What's the best defense against an aikidoka?
Answer: sweaty palms.
I'm sure a lot of people here, swept away in their enthusiasm while talking about aikido to their friends, have uttered the timeless, "Here, grab my wrist", and generally made a nuisance of themselves. Well one time my friend had very, very sweaty hands - and it totally grossed me out. It feels quite different from "normal" sweat. Needless to say, I never tried out aikido on that friend again!