Extreme Rules possesses a truly unique place on the WWE pay-per-view calendar. As the one event of the year that not only condones, but also outright encourages, radical and excessive behavior in the ring, WWE’s annual hardcore holiday might as well borrow a line from Las Vegas’ tourism bureau: What happens at Extreme Rules, stays at Extreme Rules.

Superstars, whether natural-born brawlers or competitors of the more graceful and technical ilk, have the tendency to take greater risks and dial up the danger at Extreme Rules — thanks, in part, to the slew of stipulation matches that constitute the lineup.

But with the event being a maelstrom of mayhem, that begs the question: Who is WWE’s most extreme Superstar? Which competitor is willing to go to the greatest lengths and sacrifice his or her own body in the interest of damaging their opponent’s?

To find out, WWE.com went to the experts themselves — WWE Superstars, commentators and legends — to get their opinions. The responses may just surprise you.

Vote for your choice of WWE's most extreme Superstar | How to watch Extreme Rules

To some Superstars, “extreme” is not just a wrestling style, but rather a state of mind that permeates everything an individual does.

Take, for example, the case of Sheamus. In the last year alone, The Celtic Warrior waged a war against Big Show and The World’s Largest Athlete’s oversized steel chair; he had hard-hitting battles with Europe’s top strikers, Antonio Cesaro and current Intercontinental Champion Wade Barrett; and he came as close as anybody to conquering the dogged Shield. Yet, according to fellow Superstar and former roommate Ted DiBiase, Sheamus’ extremeness doesn’t end in the ring.

“Having lived with Sheamus for a little while, I just know what he’s like. He’s crazy,” the third-generation Superstar told WWE.com. “When he trains, it’s extreme. When he eats food, it’s extreme. When he fights and beats people up, he is absolutely extreme, and I think he best defines what Extreme Rules is all about.”

The Celtic Warrior's toughest fights | Full match: Sheamus vs. Wade Barrett (Tables Match)

Similarly, The Prime Time Players’ Titus O’Neil named as most extreme a Superstar who finds adrenaline rushes both inside and outside the squared circle. The Players’ powerhouse chose a man he’s faced often in tag team action, Justin Gabriel.

“That guy literally has no regard for his body,” O’Neil said of "The Cape Town Dare-Wolf." “He does skydiving, rides trick bikes and motorcycles, and inside the ring, he’ll do just about anything as a competitor to entertain the WWE Universe. Given the opportunity, I’m sure he could show a lot more, and I know he will in time.”

It’d be shortsighted to discuss anything “extreme” without speaking to one of WWE’s top authorities on the subject, Paul Heyman. The mastermind behind the now-defunct but once-revolutionary Extreme Championship Wrestling has witnessed the ring’s greatest brawlers of the last quarter-century, from Mick Foley to Terry Funk, firsthand.

“It’s a very complicated question with the simplest answer imaginable: Brock Lesnar,” Heyman answered. “Brock Lesnar will demonstrate just how extreme he can be against Triple H in an old-school Cage Match at Extreme Rules. Who else could possibly be the answer to that question besides Brock Lesnar?”

Disregarding Heyman’s bias, The Anomaly’s associate wasn’t the only person to pick the former WWE, UFC and NCAA Heavyweight Champion. It was at last year’s Extreme Rules that Lesnar made his historic return to the ring, and although he narrowly lost to John Cena in a barbaric main event, the punishment that Lesnar unleashed on the Cenation leader resulted in a macabre scene and bloodstained canvas.

Ringside commentator and former WWE Champion John “Bradshaw” Layfield — himself a veteran of innumerable barroom brawls and steel cage encounters — joined Heyman in picking Lesnar.

“There’s not a doubt in my mind,” JBL said. “He’s an absolute beast, and I don’t see anybody on this roster — or anybody who’s maybe been on any roster — who’s as freakish and extreme as Brock Lesnar.”

On May 19, “The Beast Incarnate” will be locked inside a cage with another competitor who can lay claim to being among WWE’s extreme elite. According to sports-entertainment icon Michael “P.S.” Hayes, a founding member of The Fabulous Freebirds and presently a WWE producer, Triple H tops the list. Judging by The Cerebral Assassin’s lengthy résumé of Street Fights, Falls Count Anywhere matches and Steel Cage matches — never mind his tenacity and trusted weapon of choice — one would be hard-pressed to disagree.

“There’s a number of people high up there on the ladder, but if you pay attention to history and ruthlessness, and the willingness to do anything to get the job done by any means — using anything, including a sledgehammer — I think you’ve got to go with The Game,” Hayes commented.

Bringing the Hammer Down: Watch Triple H's sledgehammer attacks

Even beyond those aforementioned Superstars, the modern WWE roster is replete with tough-as-nails fighters who come in all shapes and sizes. There’s Intercontinental Champion Wade Barrett, the 6-foot-7 legend of England’s underground, bare-knuckled boxing circuit who seamlessly integrates stiff haymakers into his repertoire.

Don’t forget Dean Ambrose, a rambunctious and dangerous individual who, prior to signing with WWE developmental division NXT, made waves competing in small, hardcore-based outfits. A veteran of “death match” wrestling, Ambrose has participated in some of the ring’s grisliest moments.

On the other end of the spectrum, one could point to the unmistakable face of WWE, John Cena.

The reigning WWE Champion’s name doesn’t always come up in these types of conversations, but don’t let his family-friendly image and clean-cut ring style fool you: Cena can embrace the extreme with the best of them. Proof of this can be found in his stellar record at Extreme Rules and its spiritual predecessor, One Night Stand: Cena is 6-1 at these events, prompting WWE Magazine to recently dub The Champ “The New King of Extreme.”

Yet another name that finds its way into the equation is the No. 1 contender to the WWE Champion, Ryback.

Watch Ryback unleash his rage | See the Cenation leader's most extreme moments

“Here’s an individual who is so hungry and thirsty for the WWE Championship, and he stood in the ring with an extreme icon in Mick Foley, and he didn’t back down at all,” SmackDown commentator Josh Mathews noted. “I think that Ryback has that hunger right now that’s going to lead him to a WWE Championship at Extreme Rules.”

With so many options, it’s hard to select just one combatant as WWE’s most extreme. Nonetheless, many Superstars will have the opportunity to prove just how hardcore they can be when Extreme Rules airs on pay-per-view on Sunday, May 19.

Until then, make your voice heard and check out this WWE.com-exclusive poll to vote for the Superstar you believe stands out from the extreme pack.