Although I do have some personal preferences, I think that is a bad mindset to have in regard to confrontation.
The concept of having a preference takes away from the goal of improvised weapon study. The goal is to learn and understand the physical properties of every surrounding object and how best to use the mechanical advantages of the object in a given situation.
If one has a particular preference, than his/her mind will be fixated on employing that "weapon" rather than appropriately dealing with the confrontation at hand.
So, rather than having a specific preference, one should have NO preference or pre-conceptions on what to use in a conflict. Whatever is closest will be the weapon of choice because the user understands the discipline of the object as well as he knows himself.
Vladimir told me that in his unit, whenever they were introduced to a new "tool", they weren't told of it's intended purpose at first. Rather, each soldier had to write down as many possible uses that they could think of for the object. After being forced to use their creativity, they would all compare notes and learn from one another. Only after that would they be told what the device was really for. Now their minds' were not confined to a cognative "label".
That being said, I'm partial to Sharpie laundry markers myself.
-Jackal