I recently came across this video of a couple of guy trying to break through the passenger side door of an Audi A4. Apparently the Audi A4 windows are near indestructible! Watch the video to see what I mean.
I call this The Hard Way!
I also found a video where a guy breaks through a car window with a broken piece of a spark plug.
I call this The Easy Way!
So for those interested in how exactly the easy way works I will regurgitate what I have read after a little bit of searching.
"The ceramic from a sparkplug attracts negative electrons (Negative Static) A cars side or rear window (Tempered Glass ie safety glass) has positive electrons (Positive Static) If one were to throw a peice of sparkplug ceramic at a car window the first part of the ceramic that touches the window creates a miner spark explosion which temporarly weakens the glass to an extreme point than the rest of the weight of the ceramic breaks the glass." - WikiAnswer