I really like this one from a local United Methodist Church, (although not likely to show up in front of an LDS Church):
On the other hand, here are a couple that would fit in quite well at an LDS church, especially the sign as you leave the parking lot of the local John Calvin Presbyterian Church ("You are now entering the mission field"):
Another LDS type sign, since we know how much LDS folk love focussing on "self-improvement":
A little sign caught my eye inside the kitchen of the Stake Center where I attend (definitely NOT one of my favorites):
Still haven't found one to rival my favorite sign, but I've enjoyed snapping the pictures none the less.