I dunno. The life-size space marine armor from that sfx company in the UK (Nimba Creations, I think) is pretty sweet. *drool* I'd go for some live action boffer combat if I got to wear the blood angel armor.
I am actually surprised that there aren't more people who costume as 40k stuff. There's a lot of variety and most of the minis look really awesome. Understandably, some of the costumes would be really difficult, but there are plenty of others that could be done with pink foam*, a hot wire, and a heck of a lot of urethene (sp?).
Though if you do go look hard enough online, you can find some pretty hardcore fans who have made some awesome 40k costumes. I guess that isn't everybody's cup of tea, but yeah...If you haven't guessed, I'm one of those evil, evil LARPERS that you occasionally see skulking around.
*Pink foam. A high-density, but lightweight foam commonly used as housing insulation. There is also another brand which is pastel blue. You can cut/sand it to whatever shape you want, and if you seal it right, you get a lightweight, and surprisingly strong item.