[denimnerd42]

There is a steel called Corten where the rust develops a protective layer similar to aluminum and won't rust all the way through. The only issue is it isn't good when exposed to constant water as the rust will wash off and not protect.

[kibwen]

The USX Tower ("The Steel Building") in Pittsburgh is made entirely of Corten, designed to showcase the material when it was first developed. Other than turning all the sidewalks black when it was first weathering it seems to work great, as long as you're into the industrial aesthetic.

[Arrath]

Some may also find the rusted patina look less than ideal. Personally I don't mind it at all.

[denimnerd42]

some people use it as an architectural element. they'll build planters, roofs, siding, fences...