Its the one that Superman would use, so if you put your iPhone through the most gruelling of routines thanks to your job profile or commute (such as being on the Tokyo subway) then this Titanium cover sounds like the perfect buy.
The ultra durable shell (which is putting it mildly) is made from a single piece of titanium which not just makes the iPhone look great but also protects it from most abuse. The cover comes with a laser engraved logo and text as well as a non scratch internal coating.
The titanium cover retails for $120 and is available from Snow Peak. The cover is made in Japan (just so you know) and is intended only for the iPhone 4.