Benchmade folder, kubotan keychain, and several years experience in Army Combatives.
Touching on what people have already said, mindset is your best defense.
Be aware of your surrounds, have an escape plan, know what around you is cover and concealment, and know the difference between the two.
In a pinch, anything can be a weapon. A rock, glass shards, keys, your size 12 boot, anything. Preparedness is 90% mindset though.
I recommend to my friends who can't carry at work to keep a Kimber Pepperblaster 2. Very user friendly, handles like a pistol with a grip and trigger and all that. Built in belt clip for easy concealment, and it's a gel, not a spray, so there is less "spraying in the wind" effect. Obviously, it's not 100% effective, but it could provide you with enough of a distraction to get to a better weapon, or get the hell out of there.
Korey - Shamrock Armory
Glaine ár gcroí, Neart ár ngéag, Beart de réir ár mbriathar.
Purity of heart, strength of arms, and truth in words.