I thought about this for a long time, and honestly - and this will be a boring answer - the tool that makes me most successful is my ATV. I still do a lot of scouting leading up to season opener, and in the past, noticed just how jumpy older to mature bucks are about encountering human scent where people walk in the woods. However, I have also noticed these same bucks pay almost no attention to the scent an ATV leaves after it has been driven through the woods. For this reason, I now almost never scout on foot. I only scout from the back of my ATV, and the deer seem to be completely oblivious to the fact I've been there.