A guy at my work sees me riding in every morning. He's been talking about riding to work himself (he lives about 5 miles away, owns a basic MTB, rides every afternoon with his kids). This morning he finally commuted to work for the first time, and loved it. Told me I had inspired him - seeing me ride 12+ miles each way rain, hail or shine made him realize that he could ride to work too.
Nice feeling, knowing that you've played a part in helping someone else experience the coolness that is bike commuting.
Now, on to my next victim.