I remember in Halo 3 it was possible to spell things with the tiny lights at the bottom of teleporters. Teleporters are different now so I was wondering if it was possible to do something like that in Reach with a different object.
The main thing I've seen people spell with is railings (small, medium, etc.). Also, this should probably be in Reach Forge Discussion.
You can use the columns as well, they do a pretty good job. This shot has the blue overlay on it but its the only one I made letters with.