Pulling out a hobby knife is better then nothing. Many people here are throwing stones at situations they have never experienced. In regards to inflicting damage with a multitool, it would be as effective as any other knife,especially if they're unaware of your intentions to defend yourself in such a violent manner. Consider this situation, you get on a train at 11.00pm, no one else is on the train but you. You're not sitting near the guard comp and two thugs get on the train and sit next to you. They say "give all your money right now cunt or I'm gonna smash ya fkn head in", so you give them your money. After they have taken your money, phone and clothing they start kicking you and calling you names and one says "let's kill the cunt"... How unfortunate it is for you since you're not carrying your multitool. Now listen, if the situation happened to me, I would give them everything in the hope that they will fuck off, but if I was hit anywhere, I would stand up and walk off. If they followed and continued to threatn me, by then I would have my blade ready and I would aim for the neck.
Personally I'd prefer to be in a cell then a cofn, and btw if you're a student and a gud citizen, and you stabbed thugs in self defenz, hot water my fkn arse.
You just need a good reason as to y u were carrying the blade," I use for my bicycle sir. Or even to peel your oranges at school...