If you have a car that takes a key to unlock the door, have that key at-the-ready, but in your off-hand. I met a lady that had foiled an attack by using her car key to slash the face of her attacker, then she was able to quickly get in her car and get out of the area. The attacker was EASY to identify later!
Use some common sense! If you have the two men following you, but you also see a group of other people within reasonable distance, call out to them as if they're your friends. Something like, "Hey, I thought that you guys got lost! We're over here!" The least that will do will be to attract the attention of the group of people, in case something does happen.
No one else in the parking lot? Well, try a ruse distraction of some sort. Look into the sky and exclaim loud enough so they can hear you, "Wow! What the heck was that?", or something like, "Wow! I wonder who the police are chasing?". (This is sort of like the prank of standing on a street corner, looking intently into the sky, then look around to see how many others wondered what you were looking at). The distraction may give you enough time to get in your car, and be relatively safe.
Once you're in your car, it's a 2-ton "weapon".
More? Well, most business parking lots will have a few shopping carts strewn about. Ever think of those carts as "battering rams"? The least they could be used for would be to put about 3' distance between you and at least one of the attackers....but possibly swung around to smash against the other....or perhaps smashed up against a parked car, to cause a loud metal-against-metal crashing sound that might attract attention.
Of course, if you're carrying, most of these distractions will at least give you enough time to unholster and start computing "shoot/no-shoot" thoughts.