Willie the Duck
Legend
Thinking along there lines, something else that D&D certainly did not invent, but amplified and added its own influence to was just the depiction of medieval people (adventuring people in particular).It's a chicken or the egg scenario. As mentioned later, D&D absorbed a lot of myth and fantasy and regurgitated it into other media. For example, the monk class is clearly based on all manner of kung fu pop culture, but unarmed Eastern fighting types being common in all manner of RPGs from Final Fantasy to Warcraft comes from their inclusion in D&D.
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Popularized rather than invented, but even the fact druids have moved from Celtic pagan priest to generic shape changing nature mage is due to D&D's influence.
Recently Penn and Teller performed at the Minnesota Renaissance Festival to celebrate their having met there 50 years prior. This caused me to look at some picks of the costumes there from that era. I've also (because my brother's kids are of the right age) seen the Disney Robin Hood and a lot of the old Looney Toons, including the ones with Bugs and Daffy and Porky as being/conflicting with Robin Hoods or knights or whatnot.
Media from the 70s and before depicted Ye Olde Days with a lot more knights on horseback with lances and full helms with clamshell visors (of one style or another). For unarmored men, a lot of primary color two-tone garb (often crossed, with the same color on the lower left and upper right, and converse), often with tights as the legware. For unarmored women, a lot more dresses and conical hats. Lots of pointed shoes. Lots of jester outfits. Lots of livery. Wizards wore robes with moons and stars and a pointed hat.
Since then, there's been a lot of shift towards a different aesthetic. More earth tones. More leather. A lot more 'light' armor -- some of it leather or studded leather, but even just less metal armor and more form-fitting-looking stuff. More open faced helms. More footmen. Unarmored folk have ditched the bright colors and men have ditched the tights (and more women are showing more leg and certainly more women are wearing armor).
Now none of this is pure and straightforward. All of it has been around forever -- we wouldn't even have studded leather if Gygax (and his sources) didn't have existing depictions to misinterpret. There certainly was less complete (than full harness) armor used at many times/places, so this is just an expansion of what was depicted. Likewise, the trend in that depiction didn't start with D&D. Frank Frazetta and Roger Corman get as much credit as Gygax. Pulp novel covers, comics, and later B-movies shifted depiction of the era from Hollywood soundstages and the like as much of more than D&D. Still, I think D&D did a lot to help shift some of that stuff strongly towards a different look and feel.
The martial artist in particular, yeah that's hard. But moreso than other things we might mention, Akitoshi Kawazu and the rest of the creative team behind FF1 have been upfront about it being their own version of Wizardry/Ultima and a love-letter to AD&D. That's a lot more direct that much of what we have.But then you have an issue of tracing. Someone saying that, though media had barehanded martial artists aplenty for years, Final Fantasy got its version specifically from D&D, and not also from those other sources? That's a hard claim to substantiate.

