i already mentioned the sigma 12-24mm but it seems i got ignored. it's got a bit of a cult following as an architectural lens. it's also the widest rectilinear lens you can get which fits fullframe (so if you ever went fullframe you'd have 12mm!).
That's good to know, because I was sort of bemoaning the fact that if I did get say, an EF-S lens, then I'd have to sell it if I upgraded to FF camera. I will have to look into this lens. What about any Tokina or Tamron lenses? Recommendations there?
I plan on putting a thread for people to vote on this later on, so I'll include this lens in my poll and you can be sure to vote and make your voice count!
I just noticed that you put sigma 12-24, but didn't mention the other important information. That would of help me and I wouldn't have ignored it. Sorry about that!