Unlike most of the responses, doggy has actually allowed me to last longer. It is the old standby of missionary that I have always come both the fastest and most intense, maybe because it allows me the most control of the timing, depth and allowing facial contact for kissing and caressing. In fact, we will switch to that position if one of us is getting tired in another position and we want to finish up.
But overall the one true act that has always caused the most intense explosion has not been vaginal sex, but oral. I can get off in a very short time when getting a BJ.