I wish I had a laser rangefinder whenever I play a new course. There's always a couple of holes where a ridge in front of the green cuts off the bottom part of the flagstick from view. This usually leads to an approach shot that's too long because I over-estimate how far the distance is.
Our home course has on-board GPS systems in the carts, useful except on rainy days. When it's cart path only, you have to guess on "distance to center" because your cart + GPS is 30 yards away from the ball.
One thing I would use it for is calibrating my wedges... quarter, half swing, etc.