What length nails do I need to nail fence pickets onto 2x4's?

I was going to use a 2" ring-shanked nail, but thought it might poke through the 5/8" picket and 2x4" (since they generally are about 1.5" not 2'). Should I rent a coil nailer and use smaller nails? Can I find ring-shanked nails in smaller lengths than 2"? What do you recommend? And no screws....I refuse to screw in 3000 screws.