Can't afford to collect Spyderco knives, but I'm a fan. One of my favorites was the Rescue model, made for cutting seat belts and clothing of accident or illness victims. I kept in clipped to the sun visor in my car until someone broke in and stole it. It was a great design for the purpose.
I carry an Endura 4 regularly. Brown scales, flat ground plain edge, strong steel clip. Great cutting tool. It was a gift from a very generous member here.
I don't consider it a self defense weapon--that's why I carry a gun--but I'm sure it would be up to the job if all else failed.