Anything made of corn other than flaked maize CAN be used, BUT in order to do it you have to do a cereal mash to render it fermentable... The "flaking" of the maize achieves the same thing... you CAN use unsugared cornflakes or tortilla chips (baked is preferable but I've used "fried" as well in cream ales, in the mash tun the other grain absorbs the grease from the chips) in the mash tun just like flaked maize without doing a cereal mash.
I THINK, that instant polenta doesn't require it either, I think the "instant" processing pre-gelatinizes it as well, but don't quote me on that. I know someone used popped popcorn for a cream ale as well on here years ago, but I can't recall if he did a cereal mash or if popping rendered it usable as well.
Anything else, cram corn, non instant grits, cornflower, ground popcorn kernals, non instant cornmeal can all be used, and has been, but you need to do the cereal mash first....
Cereal mashing is not hard to do, but it requires an extra step... BYO has a great
article.
I just brewed this on Saturday, using Saflager again and making this a steam beer.