There are dozens of things you can pick up in an emergency and make a weapon from the object. Rocks, sticks, pipes, any other heavy objects you can bring to hand. Making something on the run is not a skill most people have or consider until they are being chased or are nearly caught in most cases. In an urban environment you might be hard pressed to locate sticks and stones or rope, chain and so forth.
You might or might not be able to “throw together” something in a bad situation, on the run. It pays to think things out ahead of time – always – and keep situational awareness in your mind at all times. You might notice there are items on the ground. You might not. This is not a dissertation on every idea or an expert paper on what you can and can’t do. Rather we will give you a few ideas to consider and show you some links and images of items others have already thought of making.
Why re-invent the wheel?