I was thinking about ways to create uncommon combat challenges in L5R to offer variety for groups that feature combat more often.
I think the rules offer a variety of scenarios that differ from how a combat usually plays out. Now, these fights need to be specially set up by the GM to avoid them being either completely unfair or easily completed with the right counter ability. I expect each will only work if certain abilities are NOT in the PCs arsenal.

A few ideas:
1) Fist Fight
Since unarmed attacks have very low damage, an interesting challenge might be if the PCs have to fight a skirmish or duel with unarmed strikes alone, whether as a barroom brawl or a boxing match.
The result is a combat that may take multiple rounds, especially if one fights in Water Stance and thus can regenerate Fatigue.
Problematic if the PCs have access to: Kiho, since that raises the damage to weapon combat levels. Also the Flowing Water Strike Kata.

2) Fighting invulnerable opponents
A very special challenge might be fighting an opponent with Resistances so high that regular damage will not break through. Thematically, that may be the werewolf equivalent of a supernatural enemy immune to most weapons that has to be pretty much hacked apart before it dies.
That fight can still be won, but only through critical hits, which ignore resistances. In the simpler version of this challenge, the resistance may be part of the opponent's armor, so two Critical Hits of Severity 0 are enough to destroy the armor and make the fight normal. In the harder version, the Resistances are an opponent's ability and thus not dependent of armor. Multiple critical hits may then be necessary depending on the PCs weapons: Two Lightly Wounded Crits become one Seriously Wounded, another Wound will cause a Scar, and another Scar of the same kind will result in Dying (5 rounds).
Problematic if the PCs have access to: Sacred or Unholy weapons or invocations (which ignore otherworldly creature's resistances), although offering an Unholy weapon as a problematic solution is certainly interesting. The Bind the Shadow invocation can prevent the encounter by just binding the Otherworldly opponent to a place, which on the other hand means the threat is only postponed.

3) Sadane fight
Sadane is the game of insult fighting, favored by the Crane courties. In a sadane fight, your words are your only weapons. Attacks may be Courtesy checks vs the target's Vigilance as TN, with success dealing Strife equal to 1+Bonus Successes, and the fight being won when an enemy becomes Compromized or Unmasks.
Wargear should not be allowed in such a courtly setting.

4) Wrestling Match
The lore tells us that the Unicorn clan likes to duel as wrestling matches. The problem is that there are no good rules for that: Wrestling should certainly mean inflicting the Immobilized condition, but since the only ways to do so in a wrestling context require the spending of Opportunities (Snaring weapon Quality or Coiling Serpent Style kata), simply fighting in Earth stance would make a fighter completely immune. Only the Silent Elimination ninjutzu technique would work around that, and very few schools can even learn that.
Even if we were to say that in a dedicated wrestling match, Earth stance does not prevent the Immobolized condition, we would we left with a fight where a successful attack is unimportant, since the Immobilized condition only requires Opportunities, not a successful attack, and thus e.g. the Air stance bonus is useless here.
It would be one way to say that in a dedicated wrestling match, causing Immobilized requires both a successful Unarmed attack AND the Opportunities to use the Snaring weapon quality, Earth Stance does not prevent that, and then having three successful instances of Immobilized as the win condition, possibly with just hitting the opponents until he is unconscious as an alternative way to win (those Unicorns can kick...).
But I have not found a great solution here. Does anyone have a good idea?
Problematic if the PCs have access to: Silent Elimination Ninjutzu, and Kiho if hitting opponents is allowed.

5) Mobile Opponents
This is not such an obscure challenge: The PC simply face opponents good at Water Stance and either armed with ranged weapons or long-ranged melee weapons like the Kusari-Gama. Since the opponents can move two or more range bands on their turn, the PC may have to dig deep in their abilities to get in range for their own attacks, with solutions from throwing weapons as improvised attacks, immobilizing foes, using kata or invocations up to only assisting the one PC with a ranged weapon or suitable Water ring.
A variation of this can play out in Concealing terrain, where opponents are only visible if they are no more than 2 range bands away, so ranged weapons are less of a solution to the opponent moving away after attacking.
The inverse would be if opponents had an ability like the Armor of Radiance invovation, where it is imperative to prevent the opponent from getting near.
Problematic if the PCs have access to: Without the Obscuring variation, PCs with good ranged attacks will not even notice the challenge as uncommon.

6) Balancing Fight
A classic in the martial arts movie canon, this is either a duel fought balancing on top of vertical poles or a skirmish fought on scaffolding. Any hit that either exceeds a certain damage threshold or inflicts the Prone condition or pushes the opponens one or more range bands calls for a Fitness check to avoid falling a number of range bands depending on the setting, with possible bonus damage if the ground is covered in blades, glass, fire etc. While falling in the Duel version of this usually means losing the duel, PCs or opponents falling in the skirmish have to move back up before they can continue fighting, so even a single opponent good at pushing targets (e.g. with the Thunderclap Strike Kata) may keep multiple PCs busy climbing while fighting just one or two at a time.
Problematic if the PCs have access to: This does not work if the PCs can just stand somewhere else and pepper the opponent with arrows.

7) Peasant Weapons
Whether as a campaign set-up or only for an adventure, the PCs could be forced to act as peasants of the bonge class. An option would be that the PCs lord orders them to enter enemy territory disguised as peasants to fulfil a quest (the GM should make sure the PCs do not regard this as impossible to reconcile with their bushido). When disguised as reasants, the PCs cannot use any armor better than travelling clothes, no swords or Wargear weapons, and not use Kiho or Invocations where they are seen by others. Hatchets, hammer or perhaps a bo staff are their means of combat.

Other creative ideas?

Regarding 2, 3 and 4:

Even you are fighting a supernatural creature whose armor is intrinsic to it, it shows as equipped gear: so stuff like thick hide can still be damaged and destroyed.

Regarding sadane, I would treat it as an intrigue conflict where the objective is to compromise the opponent.

Finally, a wrestling match would definitely be a duel in my view and thus, predict can take care of earth stance turtling.

1 hour ago, DSalazar said:

Even you are fighting a supernatural creature whose armor is intrinsic to it, it shows as equipped gear: so stuff like thick hide can still be damaged and destroyed.

Regarding sadane, I would treat it as an intrigue conflict where the objective is to compromise the opponent.

Finally, a wrestling match would definitely be a duel in my view and thus, predict can take care of earth stance turtling.

Regarding Resistances, that is not necessarily the case: the Forest Troll from the Core Rulebook, for example, gets resistance from an ability, that cannot be overcome through inflicting the Damaged/Destroyed condition. So a creature with higher resistances than the Troll is easily imaginable and in line with the rules.

Regarding wrestling, the problem with Predict would be that that is an action, and an Attack at that. So while you could predict Earth, you could not attack in the same round, even in Water stance. The effect is that you only attack every second round, while your opponent can attack every round (albeit only every other in Earth stance).

Oh, believe me, I hate the duel options. 9 out 10, attacking is best option.

Saw the Forest Troll ability. Yeah, that one definitely gives multiple interpretations. Because I could Sorcerous Scales being damaged or destroyed anyway.

I've had fun with night fighting: Everyone counts as Obscured.

Added another combat challenge: Peasant weapons.

@Tenebrae : I thought about night fighting. My problem is that Obscuring terrain alone is not much of change to regular combat: Only TN+1. One way of escalation would be giving everyone without other senses the Blind Disadvantage. Still, both are far from covering how a fight it total darkness would go, when you do not even know where an enemy is.

The rules are quiet about how long it takes to light a candle/lantern, but requiring at least 1 action with a lighter in hand (requiring hands free of weapons) seems sensible, and an attack aimed at a lantern should extinguish it. An enemy with access to the Extinguish invocation like my Chochin Obake or a group of minions with night vision (goblins perhaps) would certainly have the ability to create this kind of combat szenario.