There are so many to choose from. For me it kind of depends on the day, but over all I would have to say that Disarm is my favorite.
Yes i know its kinda of unimaginative. I suppose I could name off some rare track and seem a bit cooler but Disarm was the first pumpkins song I ever heard. I still remember where I was and what I was doing when I heard it. Now almost 14 years later, I can honestly say that at the very least it has made a lasting impression on my life. To this day I can not listen to it with out feeling the same way I did that day.