Marx 490 0-4-0, 1964 (I was not yet a year old). That engine has a small piece busted out of the pilot and the cab roof (from many collisions with friends' Marx wind-ups), but it runs like a champ every year at Christmas. On the current 045 inner loop, I can really let it stretch its legs.
I wouldn't trade that engine for any other. Thanks, Grandpa!