A simple search for Darth Vader iPhone cases on Society6 produces a ginormous collection of original art featuring the Star Wars inspired Dark Lord.
I pulled my Top 5 favorite designs from the lot including Tron Vader, Brand Wars and Darth Kitty — although "I Am Your Farmer" by artist Illograph is the one that caused instant tingling in my geeky parts.
Each artistic interpretation is printed on Case-Mate's "Barely There" plastic hard case and will cost you $35 for iPhone 4 or 4S. You'll find approximately 80 original Vader designs to choose from. Good luck with that!