If it's hard to follow this finger

Here is an ambient ad for Hapa Sushi Grill & Saki Bar:

Paper hands with an extended pointer finger were wrapped around the wiper blades of nearby vehicles with copy that reads:

When to call a cab

1.  Turn wipers on low

2.  If you have any difficulty following the finger with your eyes, we suggest you call a taxi 1.800 ....

How much water you really need

Here is an OOH campaign for Denver Water to raise awareness for water conservation:

There were several large-sized objects placed around Denver with copy that says "How much water you give your lawn."  These larger versions were placed next to "normal-sized" ones that reads "How much it really needs."

The campaign included billboards: