In Glorantha (which I know best from RuneQuest 2 and a little of RQ 3), parts of Peloria and the lunar empire engage in "Dart Wars" -- openly secret assassination to settle disputes between nobles, with strict legal controls. In Empire of the Petal Throne (the original version of the game), wars are settled in the Hirilakte arenas using gladiatorial proxies. Personally, I like these ideas, since they give a reason for amoral warriors to wander around the world, and to give some sense of danger to their presence.
In Zamora, disputes between houses can be settled in many ways. Many involve appealing to the Overlord or his courts, but these kinds of appeals can be difficult and expensive, and risk angering the Overlord for demanding his attention. Most of the time, disputes are settled through House Wars.
While open warfare between Houses is possible, it is illegal, dangerous, and brings unwanted attention. Most of the time, settling a House War is done through professional intervention in the form of hiring either a Sword-dancer or a Face-dancer.
Sword-dancers practice their trade in three ways: one is that they are performers, using their mastery of weapons in an acrobatic show and performing feats of prowess to wow the crowds. The second is that they serve as fencing instructors, particularly to those who want to learn flashy styles. The third and most common is to take on jobs as duelists (often standing in for their bosses in formal duels) or assassins. Such trade is legal, but any Sword-dancer must declare his trade openly on starting business or entering the city, and a public listing of all sword-dancers and their know residences is published once a week in the Hall of Records. Official Sword-dance contracts on individuals must also be publically logged and posted before the Sword-dancer may begin to pursue a target. It is legal always to kill a Sword-dancer who is actively pursuing a contract, regardless of who is the target. Thus, being a Sword-dancer is a very dangerous profession.
Face-dancers are less common and more subtle. Masters of disguise, seduction, deception, and poison, most face-dancers are hired to ruin people rather than killing them. Seducing people to learn secrets or to undermine their marriages are most common, though stealing incriminating documents, sabotage, and general forms of blackmail are also frequent tactics. Face-dancers are less open about their profession, do not need to post their contracts, and are seldom involved with direct violence. Instead, they enact more long-term schemes of deception, and are often more secretive and more expensive than Sword-dancers.