I lied a lot of times. In Toronto, you have to be 19 to get alcohol, and I used my older brother's ID to get drinks since I was 15, since me and him practically look like twins. I can finally start using my own ID starting this June.
I claimed I was 7 up until I was 10 (it was believable; I claimed my father was tall, so they expected me to be), and it worked, just to get on the subway/bus/train for free.
Also my parents often told me to lie about my age at buffets so they would have to pay less. When I turned 14 they had to stop because the local buffets realized I couldn't be 11 for 5 years.