What to get Dad?

Like most, I have a father who enjoys many of the stereotypical pursuits; a green lawn, barbecuing, sweets. He also has an infatuation with HO scale model trains which for years on end provided an endless source of gifting opportunities. Now, years later and 9 months from retirement my dad has amassed a closet full of unbuilt buildings and sets. So I find myself a little more perplexed on what to get the old man.
He's been a firefighter all my life an unsung public hero (no amazing 30th floor rescues or anything) but he's saved countless homes from brush fires and I imagine a family pet or two. There's a lot he doesn't talk about with his work, the tragedies, the tedium. When I was in college I did a series of ride alongs with my camera, and I learned so much about what they do, the excitement of a first fire (we had a new guy) the brotherhood of the guys (good and bad) and seeing my dad in action. He used to make a lot of comments about me joining the department. "We'd be the first father - daughter team," but he stopped chatting about that when I got married and moved to Colorado. Now, I get to watch him with my girls and remember my childhood memories, playing cars in the sandbox, going camping. Visiting dad at the firehouse and climbing on the rigs. So what do you get for the guy who has watched under a nurturing eye and helped you reach for all your dreams. - Whatever it is. I just can't put my finger on it, so I guess I'll head to Home Depot like the rest of the world and pick up that propane tank to go with the grill we got him for Christmas.