Quite often, especially in shows set in the 50s and 60s, the father figure will be a veteran. Whether he's a Standard '50s Father or an Overprotective Dad, he's capable of being a real hardcase in the right circumstances. Yes, even the Dads who appear to be nothing but creampuff can be tough guys when they need to be, and he bases it all on his years of military service.
Often this is pulled in situations where a younger (almost always male) character needs to be browbeaten or intimidated. Whether the dad was merely a Marine, or the equivalent of FOXHOUND, at some point, they'll bring it up in a not-so-casual way when they need to remind the younger character that they aren't as soft and yielding as they seem to be.
Quite a few female characters are given a Veteran Dad as an excuse for why she's tough and independent, but it can also be a Freudian Excuse if he was a tyrannical martinet who lorded over his family with an iron hand. Sometimes this allows female characters to have access to unusual skills or assets, on the assumption that senior military officers use their aviation regiments as their kid's private chauffeurs.
This effect can also happen if Dad used to be a cop, or a government agent of some sort. In comedies, it often turns out that yeah, Dad was in the Army... but he was a cook, or a file clerk, or a mechanic, or had some other less than intimidating job.
This was a Justified Trope not too long ago for American families, given the almost back-to-back nature of World War II, The Korean War, and The Vietnam War. Given the ongoing War On Terror, one can expect this trope to come back into prominence. It shows up quite often when the plotline involves The Generation Gap.
Hub McCann: "I'm Hub McCann. I've fought in two World Wars and countless smaller ones on three continents. I led thousands of men into battle with everything from horses and swords to artillery and tanks. I've seen the headwaters of the Nile, and tribes of natives no white man had ever seen before. I've won and lost a dozen fortunes, killed many men, and loved only one woman with a passion a flea like you could never begin to understand. That's who I am. NOW, GO HOME, BOY!"
In Juno, Juno's dad blatantly states that he's a war veteran. The precise war is never quite pinned down.
In Pacific Rim, both Stacker Pentecost and Hercules Hansen have served in the military for nearly two decades. Prior to K-Day and the Kaiju invasion, Stacker had served in the British Royal Air Force with his sister, Luna, while Herc was already enlisted in the Australian Royal Air Force. After that, they joined the Pan Pacific Defense Corps and eventually became the longest serving (and surviving) Jaeger pilots. By the time of the film, Stacker is the Marshal of the PPDC and Hong Kong Shatterdome; Herc still pilots Striker Eureka alongside his young son, Chuck.
Played with in William Beamon's novel The Sunshine State. Teenage Darryl is warned by his girlfriend Sandra's father that "he'd been in the Army during the war" (the war in question being the Vietnam War) and that if Darryl "got fresh", dad might have to hurt the boy. Later when he's alone with her, he jokes about the warning, theorizing that her dad (described as "round, well-padded, balding, and genial" earlier in the novel by Darryl himself) had probably been a cook or a file clerk. She hastily corrects him:
"Who dad?" she asked. "No, he was an Army ranger. He'd be dropped behind enemy lines to rescue prisoners of war and stuff. He knows how to kill people about a dozen ways with his bare hands. I saw him beat up a guy who was trying to break into our car outside of the movie theater with a rolled up magazine. You know... special forces kinda stuff."
In A Brother's Price, all of the Whistler grandmothers had been common line soldiers, descended from soldiers, blacklisted for treason, trained as thieves, and turning their hands to becoming spies. They passed this training down to their daughters, who passed it down to their daughters. The granddaughters all have military discipline, on down to the little ones, and they are well able to defend their youngest and their menfolk. Thanks to the Whistler grandfather and his odd ideas, said menfolk are also somewhat trained. Jerin Whistler benefits from this. He's a Non-Action Guy like every male in the setting, but a Spirited Young Gentleman.
Park's father from Eleanor And Park served in the Korean War, and is suitably gruff and aloof.
Howard Cunningham from Happy Days is a perfect example of a kindly, wise Standard '50s Father. But when he needed to be, he could remind his children (and he even reminded the Fonz at one point) that he'd been in the army during "the war" (it is assumed he's talking about World War II), and could still throw down if he needed to. It was later revealed that he had been a file clerk or a cook, depending on which episode you're watching.
Smallville: His military service so defines Lois Lane's father, that even she refers to him only as "The General."
Home Improvement, Jill Taylor's father is a gruff war veteran who fought in World War II and the Korea War.
Martin from Frasier was both a Korean war veteran and a retired homicide detective. This didn't come up that much in the Retired Badass way, but was simply another facet of Martin's generally masculine persona in (comedic) comparision to his more effette sons Frasier and Niles.
Played with in Mad Men. Technically, Don is a Korea veteran, and he has a Purple Heart, but the more pertinent fact about his service is that he caused the accident that wounded him and killed his commanding officer, then stole the dead man's identity and used it to desert and start his post-war life. Naturally he feels less than pure unadulterated pride when he's asked to stand up along with other veterans at a Memorial Day event and sees his kids beaming and applauding. Later, Betty's father comes to live with them and brings his grandson a box full of his WWI memorabilia, including a helmet belonging to a German he's pretty sure he killed. Don is disturbed and tells him not to put romantic ideas about war into Bobby's head. In Don's other life at the office, his best friend Roger Sterling never misses a chance to brag about his WWII service—he served in the Navy in the Pacific Theater—particularly to young Smug Snake Pete Campbell. It gave him a virulent hatred of the Japanese that seriously threatens a deal with Honda at one point.
On 3rd Rock from the Sun, Mary's father is a WWII veteran. He bores everyone except Sally with his war stories. Hilarity Ensues when he and Sally decide to hook up (note he's still married).
In The Monkees episode "The Chaperone", Davy tries to date the daughter of a military man, but has a difficult time finding time alone with her because he runs his household like a barracks.
The Red Green Show once featured an advice segment for what to do if there was no war when you were the right age, yet people still expect a war story.
In Supernatural, John Winchester was a Marine Corporal in Vietnam, home again some time in his early twenties to marry his sweetheart. We know him as the hard-bitten, driven Crusading Widower who raised his two sons in a kind of traveling boot camp, so it's quite a shocker when Time Travel in season four reveals that he came back from the war still a cheerful, outgoing young fellow. Whose idea of a date was apparently going out for milkshakes.* This time travel is not to the fifties. It is to 1973. The Marines may have given him the tools to kick ass with, but the Bad AssBlood KnightThe Stoic hunter thing was all him and his vendetta.
In JAG, Harmon Rabb's dad was naval aviator who was MIA in The Vietnam War. Also the series' Team Dad, Rear Admiral A.J. Chegwidden, served as a Navy SEAL in the same war. Sturgis Turner's father, Chaplin Turner, also served in Vietnam.
And in the Spin-Off, NCIS, Leroy Jethro Gibbs was a Marine sniper and fought in the invasion of Panama and the First Gulf War. And his father flew a P-51 in WWII.
On 30 Rock, Liz's father was stationed at Pearl Harbor... during the Korean War.
On It's Always Sunny in Philadelphia, Frank tries to come across as this, back when he still thought he was Dennis and Dee's dad, mentioning the time he spent in Vietnam. Dee points out that Frank went to Vietnam as a civilian, in The Nineties, to open a sweat shop.
Actor Gerald McRaney often played Vietnam War veterans or other military character; with the example best fitting this trope being his role on Touched by an Angel spinoff Promised Land as Vietnam veteran Russell Greene.
The music video of Twisted Sister's "We're Not Gonna Take It" featured Mark Metcalf essentially playing Neidermeyer-turned-father, who runs his house like a disciplined army, and carried an M16, and is just disgusted at his worthless, weak son's choice to play that sick, twisted, electric TWANGER (a guitar).
In World in Conflict, Captain Bannon's step-dad (a comrade in arms of his late actual father) is a retired veteran who constantly belitters Bannon for not being a good enough soldier, even in situations where Bannon couldn't do anything.
In Hey Arnold!, Gerald was raised on the idea his father, a paper pusher, was a war hero. Turns out he was a clerk in an in-country office during Vietnam. That said, he did save a man's life when he found a wounded soldier in the field on a trip and saved his life using the files he was transporting as an emergency med kit.
Louie's dad in Life With Louie was very quick to remind everyone within earshot he served in the second world war, though his story changed with every telling. For example, he was apparently at both Omaha Beach AND Iwo Jima. The truth does come out eventually. It turns out he served in the army as a cook, with the nickname "Keister."