well, from what i've seen looking around on the boards, anything with muscles can be used really, Superman, Batman, Rambo or probably even the Fantastic 4 outfit.
Use your imagination and you'll probably be able to figure something out to suit most budgets. Heres a link to a site about one guys Pred project.
I have one of those suits maked by DB. It fits nice and very comfortable. I would use something with a light color, do to the fact you have to paint over it with a light color. Red is not a good color to paint over. I would try to find the cheapist one i could find. Ebay is a good place to start the search.
That's the one I used. It looks similar to the Superman one, but it had the least conspicuous chest logo I could find. You can see my progress with mine here.
The chest is a semi-rigid foam, which seems like it would hold its shape much better than the stuffed chest pieces. The only downside is that it'll hinder movement a little and it got a little stuffy, but I'm gonna cut a few ventilation holes under the armor to help it breathe better.
I buffed off some of the chest logo with a Dremel then painted over it the rest of the way.
The results weren't perfect, but I think it looks darn good!
Let me know if you have any questions!
Looking at the Superman again, it looks like the emblem may just be glued on, so it may come off easier *or* it may leave a gluey mess on the chest... Hmmm...