I have a clear plastic protector thing that
fits at the front edge of the bonnet, I don't
have it on the car because I think they look
dorky and mess up the airflow. It came with
my car when I bought it. They are common
thing in Australia, lots of people fit them
and headlight protectors.
They get dirt and leaves, etc in behind them
and look crappy anyway. See the third pic
down on this page for an example fitted to
a Ford Falcon
http://www.presidentford.com.au/pf_fibp_new.htm See a Toyota Avalon wearing one here
http://www.nowratoyota.com.au/passenger/avalon/accessories.html