If you do decide to carry a knife or other "deadly weapon" type item in your glove compartment, please, for your safety and mine, if you ever get pulled over, tell the cop straight up front that there is a knife (ice pick, hand grenade, etc.) in the glove compartment BEFORE you reach over and open it up to grab your proof of insurance or registration!
Girl I went to the academy with stopped a guy one night. When he reached into his glove box for his registration, he picked up his personal defense ICE PICK to get the registration. It took him a while to figure out why the nice lady officer had her duty weapon stuck in his ear and was yelling at him to drop the weapon.
Everything turned out OK, he dropped the ice pick and explained why he had it in the car, she wrote him his speeding ticket and sent him on his way (with his ice pick in his trunk, now.)
Dave