Excerpt from the novel Dead Beat -

"It's based on Code Duello," Bob said. "Well, technically it's based on much older rules that eventually inspired the Code Duello, but that's just chickens and eggs. Ortega is the challenger, and you're the challenged."
"I know that. I get to pick the weapons and the ground, right?"
"Wrong," Bob said. "You pick the weapons, but he gets to choose the time and location."
"Damn," I muttered. "I was going to take high noon out in a park somewhere. But I guess I can just say that we'll duel with magic."
"If it's one of the available choices. It almost always is."
"Who decides?"
"The vampires and the Council will pick from a list of neutral emissaries. The emissary decides."
I nodded. "So if I don't have it as an option I'm screwed, right? I mean, magic, wizard, kind of my bag."
Bob said. "Yeah, but be careful. It's got to be a weapon that he can use. If you pick one he can't, he can refuse it, and force you to take your second choice."
"Meaning what?"
"Meaning that regardless of what happens, if he doesn't want to fight you in magic, he won't have to. Ortega didn't get to be a warlord without thinking things through, Harry."

....

"Um. Okay. Look, I haven't exactly chosen a weapon yet, either. If I-"
"Simply choose one, Mister Dresden. Will, skill, energy, or flesh."
"Wait," I said. "I thought I got to pick swords or guns or something."
Ivy shook her head. "Read your copy of the Accords. I choose what is available, and I choose the ancient ways. You may match wills with your opponent to gauge which of you is the most determined. You may match your skill at arms against his, each of you with weaponry of your individual choosing. You may wield energy forces against each other. Or you may challenge him to unarmed combat." She considered. "I would advise against the last."
"Thanks," I muttered. "I'll take magic. Energy."


Failed Lynches and the Code Duello
Yes, a lynch can fail. When the hammer vote is cast the hammer’s RPS and the lynchee’s RPS are compared, no stats involved. If the hammer wins, the lynchee dies, end of story. If they are tied or the lynchee wins, that person may challenge the hammer to a duel. They have up to 24 hours after the hammer vote has been cast to issue the challenge, along with their ‘choice of weapons’, which is first choice and a second choice of the attributes, if they don’t get the challenge issued in those 24 hours, along with weapon choice, they forfeit the duel and die. The hammer can accept the duel or withdraw their vote, in which case play continues with the lynchee hanging on at L-1 and that player who cast the hammer vote can’t vote again for them that day. If the hammer doesn’t accept the duel within 24 hours of it being issued, he forfeits the duel.

Once the lynchee has issued the challenge with their first and second choice for weapons, the hammer can accept the lynchee’s first choice, or decline it and the second choice is automatically selected. So if the lynchee, or challenger, picks Energy and Skill, the hammer can accept Energy, or they can decline it and the duel will go to skill, they can’t decline that. Both players NB the mod rock, paper, scissors and the outcome of that RPS adds on to the relevant attribute for the duel. As the day is still proceeding both combatants and surviving players may continue to talk, offering suggestions, cheerleading, lying through their teeth, etc.

Outcome for the duel: If the hammer’s score ties or exceeds the lynchee’s score, the lynchee dies and the night phase is entered, done deal. If the hammer loses, night phase is entered, neither duelists dies, but the hammer owes the lynchee one ‘boon’. This boon takes the form of one question sent via NB to the mod and the hammer, to which the hammer must answer truthfully or decline, if they decline they may not target that player with a night action that night, nor vote for them the next day. Either may divulge what the exchange was, or lie about it, but they may not quote those NBs. The list of approved questions are:

What is your name?
What is you score in (pick an attribute)?
Did you take a night action on (pick a night)?

So the risk to a hammer from a duel is small but real, they can’t die from it directly but it can result in a serious disadvantage particularly if the lynchee is clever. The lynchee basically goes in to it with a 1 in 3 chance of being killed outright though (as opposed to a 100% chance of dying normally involved in a lynch) but a decent chance someone might be wary of hammering them or withdraw the vote rather than accept the duel. All things being equal the lynchee has less than even odds of surviving the duel too, in terms of pure randomness (though they get to choose weapons) and if the hammer withdraws their vote by declining the duel, someone who wants you dead and feels pretty confident might unvote and ask a non-voter to vote so they can hammer you and go for the duel. Keep in mind that stats are primarily character driven, not role related, and everyone has that ‘free point’. Also keep in mind that if you win a boon, and the hammer chooses to answer you, nothing is stopping them from stabbing you in the eyeball that night if they have a NK, or voting for you the next day with a better idea of what your strengths are, or telling everyone that they had rock as their RPS choice and so you can’t be scissors or you’d be dead, albeit it telling that truthfully makes them pretty vulnerable. There's no limit on the number of times this can happen in a day, beyond that a person can't vote again that day for someone they hammered, so you can literally dogpile someone via repeated challenges by various players. Keep in mind though that if they survive to challenge someone for a duel, and win the duel, the day ends. You can only dogpile if hammers withdraw their vote rather than duel.