Here is a story for you!
Reading this thread in what is a pre-emptive strike, I thought I might tell you what happened to somebody who also practises Aikido.
This person was travelling home from training one evening in a subway train when he noticed 3 men whom had obviously been drinking were staring at him (the train was otherwise empty). I guess he sensed trouble when they started pushing each other round as a prelude to beating him up. They started to advance, but before they were able to reach him and he took out a rubber training tanto from his kit bag (the type which is moulded to look like a knife and has a silver painted end) and struck each of them in the chest just like you do in randori. This happened as the train pulled into a station and he then ran out of the train. He looked back to see the three of the completely unharmed but stood in shock, arms open, examining their chest for the wound.
When I heard this I thought it was pretty funny, and whenever somebody says pre-emptive strike I think of this.