Bleach Black had an amazingly cool iPhone 4 case they call the Death Roll, which I believe they are going to mass produce and start selling. However, in the mean time this is a very easy, simple, and inexpensive DIY project.
Well will only need a few things. First you will need an
Eigertec Silicone Case Cover Skin for iPhone4, $6.95 on Amazon or any case you prefer, but it must be silicon so you can make holes in it.
Second you will need spikes. These come in array of shapes and sizes, so choose the one you like best. The best place, and most affordable, to get spikes is Studs and Spikes.
Next you will poke holes into the case about 4-5 rows across and 7-8 rows down. It's probably a good idea to place the studs on the case first to see what type of spacing you will need for the holes. After you have spaced out and punched the holes (with a nail or something) you will screw in the studs. And presto! A custom DIY Death Roll iphone case :)
Would you rock the Death Roll iPhone case?
PS: You can also do this with older models of iPhone and Blackberries. Just get a silicone case for that model and you're good.