The Underwear of Power that is still standard attire for the majority of male wrestlers. A remnant of pro wrestling's origin back during the day of circus strongmen, there was a time when it wasn't uncommon◊ for men to wear swim trunks like that. However, fashion and culture have changed so much that it looks odd. It seems to survive purely as a rolling throwback to the previous generation. Whenever asked why they still wear them (since, issues of modesty aside, there have been cases of things moving or falling out during a match,) wrestlers such as Randy Orton and Wade Barrett say they wear them because their idols "Stone Cold" Steve Austin and The Rock wore them, and likely someone in the next generation will wear them because of the likes of Orton and Barrett. Obviously plenty wear them for Fanservice reasons too.
The title Professional Wrestling is itself an artifact of the turn of the 20th century. Looking to distinguish itself from traditional Greco-Roman and Freestyle Wrestling, promoters coined the term. While in its earlier days it bore a closer relation to what would become known as "amateur" wrestling, it no longer has any connection to "real" wrestling (other than some grappling maneuvers being based on real holds), yet it maintains the moniker of "professional" and true wrestling is still labeled as "amateur" (which is itself in turn an artifact).
Vince McMahon has made many attempts to get away from the name (though for different reasons, mostly due to the public Unfortunate Implications of the name) and rebrand it as "Sports Entertainment," going as far as banning the terms wrestling, wrestler, etc from WWE. It has not worked, and is still professional wrestling (or rasslin' if you're feeling cheeky) to both wrestling fans and the general public/media. This is partially because of the terminology itself. Every sporting event that ever sold tickets did so in the name of entertainment for example, so "wrestling" is still the only word people know to distinguish it from all other sports.
Artifacts are fairly common within the actual wrestling itself, as well. For example, in Japan in the past, matches often started with an extended feeling-out period of ringwork, gradually proceeding to the main body of the match with lots of high spots, "fighting spirit" spots, and near-falls. To this day, wrestlers with experience in Japan will often do a token wrestling sequence to start the match off, which is really out of place when the rest of the match is a wild brawl. This may be a deliberate attempt to build up to those points in a match, starting out slow to add to the drama and to keep the match well paced. In that context, it seems about as out of place as the less exciting parts of any beginning of any movie.
Having a timekeeper is a remnant from when the matches had time limits - and were declared draws if the time ran out before either wrestler had scored a fall. If a match on TV has a time limit in any way then the time will be kept via an on-screen graphic. So the timekeeper is just there to ring the bell at the start and finish of every match purely out of tradition. In most smaller indie promotions, the ring announcer may double as the timekeeper too.
The Charlie Brown from Outta Town trope. During the US territorial days, masks were very common up and down the card (do you want your neighbors to know you're losing to the promoter's kid this week?). Nowadays, with merchandising concerns and possible movie deals, no one wants to hide their face anymore, so any "masked" wrestler really stands out much more. Of course, Masks are still the biggest deal in Lucha Libre, and transplants like Rey Mistirio Jr. would lose much of their identity without them (as proved by his unmasking in WCW. Many who otherwise consider de-masking Serious Business are willing to go along with "Rey Mysterio" being a separate masked entity from "Rey Misterio Jr." simply because of how poorly the whole thing was handled.)
Rey Mysterio Jr. himself is an artifact of WWE's once prominent light heavyweight/cruiserweight division. The cruiserweight division entertained fans for years, but someone or multiple someones in WWE management simply doesn't like smaller wrestlers, and so the division was gradually phased out. Mysterio, however, was so popular that he managed to overcome the anti-cruiserweight sentiments and remain a tremendous draw. Rey later became heavyweight champion, not because of his weight but because of his popularity.
Announcing that a match is "one fall" is an artifact to the days when there were many matches that were best of three and they made sure to let the audience know which kind of match it was (so they could pop accordingly). Nowadays, two out of three falls is more the exception than the rule, yet it is still announced this way out of tradition.
As of the curtain call Professional Wrestling itself is an Artifact. In spite of every smartass douche who will yell out "FAKE!", wrestling fans are not only well aware that the show is staged but some(though not many) even know how it is staged to a disturbing degree and are still willing to suspend their disbelief, just as anyone would while watching a movie or TV show.
Brass knuckle title belts were veering towards the artifact when the American Wrestling Association was founded, given how rarely anyone ever got disqualified for punching another pro wrestler in match at the time but they really became the artifact in Frontier Martial-Arts Wrestling, being the trope namer for Garbage Wrestler where disqualifications of any kind were virtually nonexistent. FMW had and kept multiple Brass Knuckle Divisions simply because they were too popular with the audience to do away with, though they eventually found away to drop them via heel authority figure Kodo Fuyuki, who wanted to turn FMW into a "sports entertainment company".
Wrestling schools around the world that were founded or co-founded by famous wrestlers keep advertising the fact long after said wrestler leaves. Most famously, the Hart Brothers wrestling school was run by former Stampede Referee Ed Langley rather than the Harts, much to the initial disappointment of Chris Jericho and Lance Storm (the latter being an aversion in his own school). A modern example is New York Wrestling Connection, advertised as overseen by Mikey Whipwreck, but in fact managed by former independent wrestler John Curse.
When Steve Austin was in WCW, he wrestled as a pretty boy named "'Stunning' Steve Austin", and used a finisher alternately called the "Stun Gun" or the "Stunner". When he entered the then-WWF, he abandoned both the nickname and the move. A few months later, he adopted his more famous "Stone Cold" persona, and started using a different finisher called the "Stone Cold Stunner". Could be just a coincidence, but it's also possible it was named by somebody who was used to calling Austin's finishing move a "Stunner", which would make it an indirect reference to his old gimmick.
Triple H's original gimmick was "Hunter Hearst-Helmsley", a snobby blue-blood, hence his finisher being called the 'Pedigree'. Despite mostly dropping the "character" in 1997, the move still retains its name. Still, wrestlers who want to get his attention address him as "Hunter", he once offered kayfabe financial support to a bankrupt Shawn Michaels and he referenced a match from his blueblood days where he got squashed by Ultimate Warrior in the buildup to his Wrestlemania 26 bout. His last name of "Helmsley" is often mentioned a lot as well, especially during his time as the leader of the "McMahon-Helmsley Era" for obvious reasons.
In a similar situation to Triple H, the name of Kofi Kingston's finisher 'Trouble in Paradise' is from his original gimmick of a Jamaican stereotype. While this was dropped in 2009, he kept the name. Even his name is a reference to Kingston, Jamaica, which he's no longer billed from.
The names of Too Cool (Brian "Grand Master Sexay" Christopher and Scott "Scotty 2 Hotty" Taylor) are an artifact to their days as Too Much, an Ambiguously Gay pretty-boy team. More specifically, very early on the Too Cool gimmick was supposed to be "Too Much capitalizing on urban fashion and popularity with obnoxious results." Too Cool ended up turning face in short order and the pretty-boy aspect of their gimmick was never mentioned again... aside from the fact that Grand Master Sexay and Scotty 2 Hotty continued to use those names for the duration of their WWE careers.
Hidenobu Ichimaru's controversial Re Tool of Yoshimoto Women's Pro Wrestling Jd' into JD Star in 2003 was part of an attempt to avert this trope, as the promotion itself had become the artifact after Jaguar Yokota decided to become a freelancer. The whole thing existed to give her work and put her over.
A wrestler might keep their original theme music even after switching gimmicks or changing their persona, because they're still so heavily associated with it:
Teddy Long once managed a wrestler named Rodney Mack, but that ended in 2003. He continued to use Rodney Mack's theme song, which starts with the line "You know it's the Mack militant", until his release in 2014.
Despite his theme song, Shawn Michaels hasn't had a "sexy boy" gimmick for a long time.
Trish Stratus kept her Lil' Kim "Time To Rock and Roll" theme after her Face–Heel Turn. The lyrics talked about her underdog rise to the top as a model-turned-wrestler but didn't quite fit with her heel character.
Randy Orton hasn't heard voices in a good few years yet his Rev Theory theme song informs us he does each time he makes his entrance.
Chris Jericho's countdown and explosion in his entrance theme was a reference to the Y2K countdown (hence the nickname "Y 2 J") but obviously younger fans don't get the reference.
Natalya continues to use the Hart Dynasty's theme music despite the stable splitting in 2010.
Edge's "You think you know me?" motif was from his original loner gimmick way back in 1998, yet has been inserted into all of his entrance themes, even after becoming a 15-time tag team champion and being a part of several stables, teams, and alliances.
Brodus Clay's theme song originally belonged to Ernest "The Cat" Miller, who had a very short stint in WWE in the early 2000s. The theme song still has Miller's old WCWCatch-Phrase, "Somebody call my mamma" in it.
Rikishi kept the first Too Cool theme tune for solo appearances, whereas Scotty Too Hotty kept their second one "Turn It Up".
Rey Mysterio was originally associated with rap music and baggy pants during his unmasked period (specifically with Konnan and their group the No Limit Soldiers), but kept both these things when he re-masked, even performing a rap theme of his own on WWE Originals. The baggy pants were at least a way of covering up his knee brace he wears due to injury, Rey having previously worn tights.
Edge also wore a Badass Longcoat during his brief "vampire" period in the late '90s with Gangrel and Christian, probably as a nod to the Marvel Comics vampire superhero Blade, who was in an enormously popular movie at the time. He did phase out the coat as the years wore on, but he was still wearing it after the final Blade movie (which, coincidentally enough, featured Triple H!) left theaters in 2004. And as late as 2006, he incorporated "Goth" imagery into one set for The Cutting Edge (a black table with chains and gargoyles on it).
Cheerleader Melissa hasn't been a cheerleader since maybe 2004. While she was still training to be a full fledged wrestler, she debuted as a cheerleader-valet for a tag team with a hockey gimmick called the Ballard Brothers. After a stint in Japan she stopped valeting. She's tried renaming herself "The Future Legend" Melissa, and just plain Melissa, but it never seems to stick. She has managed to find some success using the name Alyssa Flash which was what she had in TNA. She uses Alyssa Flash in River City Wrestling but sticks as Cheerleader Melissa in promotions such as SHIMMER for originality's sake. She originally brought pompoms down to the ring with her in her early SHIMMER days but no longer does it.
With the death of Shinya Hashimoto in 2005, Pro Wrestling Zero 1 became the artifact, as it was yet another example of a promotion created to reestablish a wrestler's career. Perhaps for the better, no effort was made to drastically retool it, as it outlasted the Jd' brand.
Kane has been this for several years already. Although he's fairly popular with the fans and a solid, reliable big man worker for the company to use, he rarely gets any angles, and the few he does always seem to stick out as somewhat out of place. Not only that, as he usually never ends up in a main event title feud anymore, Kane is sort of just...there. Even the fact that he's (kayfabe) the Undertaker's brother has not seemed particularly relevant since the mid-2000s, and certainly is not now that the Undertaker has retired from in-ring competition. The problem is that he's stuck in a place between solid mid-carder (like William Regal) and main event wrestler, and due to his popularity, the writers just don't know what to do with him at times.
Speaking of Kane, one of the few things that sticks to his legacy and that of professional wrestling as a whole... is KatieVick. It's been over a decade and people still bring it up from time to time, and will probably continue to do so for a looooong time.
El Chico Illegal Chicano, a great gimmick in Puerto Rican feds such as the International Wrestling Association and WWC. In Mexican feds such as AAA, it's definitely the artifact.
The "Bradshaw" in John "Bradshaw" Layfield comes from his early days in the WWF as Justin Hawk Bradshaw and later when he was just Bradshaw in the Acolytes. Likewise his finishing move the Clothesline From Hell, comes from his day in the satanic themed Ministry of Darkness. The move has been renamed to "...from Texas" or "...from Wall Street" occasionally but reverts back to the original name shortly thereafter.
But perhaps the greatest example going today is John Cena. He continues to use his famous rap anthem "My Time Is Now" (off of his 2005 album You Can't See Me) as his entrance theme and to wear baggy shorts, even though he hasn't otherwise played up the rap stereotype since about 2006.
The "You can't see me" gesture prior to the Five-Knuckle Shuffle is also a remnant of his old freestyle gimmick (which is weird because the names for the F-U and STF-U had to be changed to be more kid-friendly while the Five-Knuckle Shuffle, which is arguably even more vulgar than either of those, remains intact).
Cena's spinner WWE Championship belt. It was originally part of his rap gimmick in 2005. By the end of 2007, the center plate no longer spun. By 2008, John Cena was not even on the same show where that particular belt was typically defended, and he even challenged for (and won) the World Heavyweight Championship. From 2009 to the present, Cena has challenged for the belt, but it still no longer spins. The belt's center plate has in 2011 spun only for The Miz to spin the "W" symbol upside down into an "M". The belt hadn't served its original purpose for a long time, but was kept around mainly due to its merchandising success, before finally being replaced in early 2013.
In between his run in Ring of Honor, Colt Cabana worked in the defunct Wrestling Society X with the hilarious gimmick of Matt Classic, a faux artifact so to speak, who was supposedly a wrestler who woke up from a decades long coma and used the same techniques that made him champion in the early days of pro wrestling. His move list included the airplane spin, a slam from the first rope, and the abdominal stretch. He has also used the gimmick in CHIKARA.
The NWA Historic titles of CMLL. The EMLL Welterweight title was established before the existence of the NWA in 1934 but came under NWA oversight when EMLL joined the Alliance. When NWA decided it and the other belts baring their name would no longer be exclusive to what had now become CMLL, CMLL created the historic belts in 2010 to serve the same purpose. CMLL had since established it's own "World" titles in the same divisions, so the historic belts provide a reliable way to ensure it's own internal hierarchies since CMLL can no longer guarantee the holders of the original belts will be on their shows and the Mexican national titles were also not exclusive to them, their 'legitimacy' coming from being owned by athletic commissions in Mexico. That 'NWA' is still in the historic titles and the recognition of all the holders of the original belts is what really pushes it into artifact territory.
Layla El when she was in LayCool with Michelle McCool had the Catch-Phrase "Famous and Flawless" and wore ring jackets and t-shirts with those words on them. Even though LayCool split in 2011, she still wore the word "Flawless" on her ring gear.
Inverted in another case. She started to wear infinity symbols on her ring gear for no apparent reason. It wasn't until 2013 that it was revealed she called one of her moves The Infinity.
She's an interesting case in that while her character has more or less stayed the same, to some extent her clothing is an artifact. Her original couture was a woman's business suit, quite similar to what Stacy Keibler wore during her managing days. When she turned face and Summer Rae replaced her as Rusev's manager, Summer inherited the look. And Lana, having become an item with Dolph Ziggler, started sporting what looked vaguely like an '80s mallrat/Valley Girl look (denim jacket, belly-button shirt, miniskirt, and long blond ponytail), apparently to match with Ziggler's similar retro style ('80s Hair and Miami Vice-inspired patterned tights). After she turned heel again and reunited with Rusev, though, she continued to sport the Ziggler look. She soon got rid of the denim jacket and unbraided her hair, but retained the rest of the outfit. When she split from Rusev for good (despite the two being married both in kayfabe and in reality) she adopted a new gimmick, that of a high-class exotic dancer in a revealing spangled gown, but...
...she continues to speak in a Russian accent, despite Rusev (who has been retconned as Bulgarian anyway) no longer being one of her defining attributes. What makes this even more quaint is the public acknowledgment that the actress-wrestler who portrays Lana, Catherine Perry, is not Russian but American, and speaks as her real self on Total Divas while still being called Lana. (Amusingly, she inverted this when, during an in-character televised interview, she remarked on how easy it was to fake American accents, and then spoke in an exaggerated inflection of her own voice.)
In 2006, Jamie Noble formed a tag team with Kid Kash called "The Pitbulls"; they entered arenas to the sound of dogs barking and wore spiked collars to the ring. The team split up rather quickly when Kash left later that year, but Noble continued to use the barking entrance theme and display a cartoon pitbull on his tights all the way up until he retired from in-ring action in 2009.
Dragon Gate has a number of examples among their longest-tenured workers:
Masato Yoshino had a Tarzan-inspired jungle hero character when he first started wrestling, and then later was a fake Italian as a member of the Italian Collection. For one thing, he kept his long hair and continued to dress like the "sexy Tarzan" in ItaCon. For another, despite having shed both of those gimmicks long ago, many of his signature moves' names still refer to them — From Jungle, Torbellino, and Sol Naciente for instance.
Ryo Saito debuted with a cyclist gimmick, with a complicated finishing hold called the Cycling Yahoo. Though it was changed to "Dancing Yahoo" for a time, it's called the Cycling Yahoo today, many years after Saito last carried a bicycle to the ring.
Genki Horiguchi originally debuted as a surfer. One of his finishers, a back-to-belly piledriver, is called the Beach Break. In fact, because Horiguchi was the first wrestler to make regular use of the move as a finisher, many wrestlers even outside Japan (e.g. Fire Ant of Chikara)) call it the Beach Break. However, Horiguchi hasn't been a surfer for nearly a decade and a half.
Naoki Tanizaki was also a surfer character, sporting shorts in the ring and using a surf rock theme called Shining Wave. He still wears shorts and uses a version of the theme despite having no association with surfing anymore.
Jeff Jarrett kept the guitar from when he wrestled in WWF as a country singer who would angrily bash people over the head with it and kept doing so after dropping the gimmick in WCW and future ventures.
Why does Mark Henry have "WSM" (for "Worlds Strongest Man") on the back of his singlet? It's a callback to a tag team he had with MVP, who wore the letters "MVP" on the back of his ring gear. The team broke up after a few months, and MVP went to wrestle in New Japan during 2010, but Henry kept the letters on his ring gear.
The holding company behind WWF used to be called Titan Sports. The name was phased out during the late '90s and had been completely removed by the time the whole company changed name to WWE in 2002, but the large screen on the stage is still referred to as the "Titantron".