Having experienced only Ki Aikido, I went to watch another style of Aikido last night and was surprised at some techniques I saw.
The Sensei was demonstrating a few Tanto techniques, and I'm sure that they were helpful as extensions of the empty handed versions. However, they were described as responses to when you have someone place a knife to your back when you are taking money out of the cashpoint!
I understand that the Sensei was simply trying to add a sense of realism to the class, but I sat there thinking that I would teach a different technique in response to someone who brings out a knife and demands all of your money. I call it:
Give Them your Frickin' Money!