A metal plate, in case the assassin has a gun.
Other than that, nothing. I've a lot of karate experience and on Monday I'm signing up for aikido.
...Then, I can pretend I didn't understand the lesson about "not hurting your opponent" and break his/her arm off.
Or just my katana and/or Persian dagger. One of them looks real enough to cut you, the other one is pointy. And CAN pierce skin, very easily.