Stand-up striking is an area where St. Pierre may actually be a bit overrated. He certainly throws impressive looking strikes - Superman punches, spinning back kicks, etc. - but his numbers don't rank him near the elite strikers in the game. St. Pierre lands 43% of his stand-up strikes, which is above the fighter average of 35%, but nowhere near the accuracy of Anderson Silva, who connects at a rate of 70%. He's only knocked down two of his opponents (Matt Hughes and Jay Hieron), and as Serra proved, he can be knocked out.
One exceptional thing about St. Pierre's stand-up, though, is the way he mixes up his targets. Most fighters overwhelmingly focus on the head, throwing about five head strikes for every strike thrown to the body and legs. A serial headhunter like Wanderlei Silva will throw nearly 10 head strikes per body shot. The consequence is that this makes their striking patterns more predictable and easier to avoid. St. Pierre's striking is less predictable, as he throws only 2.3 strikes to the head per attempt to the body and legs.
However, it is on the ground where St. Pierre's striking is strongest. Utilizing a relentless ground-and-pound attack, St. Pierre connects on 60% of his heavy strikes and lands them at a rate that is twice that of the average fighter.