I LOVE D&D! But I just don't know if I would put ANY of those on my bumper. Most people either wouldn't get it, or the only one they would get "I played D&D before it was cool" just isn't true. Us D&D players are NOT considered "cool" for gaming, unless by other gamers, but we are considered cool for all of the rest of our qualities by our friends. Again, not BECAUSE we play, but for who we are.
Now if they had one that said "Sigil is where it's at", I really would consider buying it.
-MirrorMask