If you're interested in the full breadth of Tom Selleck's body of work as an actor, there's no better place to start than his earliest television work in commercials. This includes this early Pepsi spot from sometime in the 1960s (via YouTube).
Selleck seemed to hit a kind of sex symbol status right out of the gate, appearing in a shower scene in a Safeguard deodorant commercial along with fellow future stars Patti Deutsch, Teri Garr, and Penny Marshall. It's somewhat surreal to watch an old deodorant ad that features not just one or two but four performers who would go on to notable screen careers. He pulled a similar trick with Farrah Fawcett in 1972, appearing in a romantic Dubonnet spot just a few years before her own meteoric rise to superstardom.
After Selleck became a star, the commercial gigs quieted down some. But he still took the time to appear in a commercial for the National Guard in connection with his own time in the service, and in the early '90s, he was the voice behind the fondly remembered AT&T commercials that eerily predicted the future.
Now, as an elder statesman of the screen, Selleck has used his familiar and comforting voice to sell various products, and now he can be seen selling reverse mortgages even as he stars in "Blue Bloods" on CBS. He probably won't be remembered as a TV commercial fixture, but they have been a part of his career at pretty much every step of the road.