The standard option is hot-dipped galvanized nails, which provide more corrosion-resistance than electro-galvanized or hot-galvanized materials. The most reliable material for pressure-treated wood is stainless steel. Use 6-d (2-inch) rink shank nails to fasten pickets and infill boards.
I have several Porter Cable nail guns (framing and finish nailers) which have given. Finishing nails are not satisfactory for fence panel boards.