iPhone 4. To the left, to the left... okay well maybe not.

According to Apple insider, you may lose your calls more often if you are left handed than right handed.  That really slick looking metal bar around the phone and the metal piece on the right side of the phone  may be the problem.  If you cover that area or even just touch it which is the point where the two antennas meet, the phone can lose the signal and drop your call.  Source

Everyone at Apple must be right handed.