There are some misconceptions arising in this thread, primarily because the nature and conventions of duelling changed according to culture and period.
Firstly duelling was not just about honour. It was also used as an effective way of extorting wealth or leveraging political influence. This started in the Viking period, with professional hólmganga warriors... and they only carried on an older Germanic tradition.
Secondly its a fallacy to think Renaissance era pistol duels were more dangerous than sword duels. The fact that duelling was banned across much of Europe prior to the advent of pistols is proof enough of its fatality rate, many sword duels actually ending up with both combatants run through and dying of blood loss or sepsis.
Thirdly the time period of the pistol duel is very important, since early pistols were horribly inaccurate (in fact hand guns in general are still very inaccurate weapons especially when used under stress). Instead of a duel being ended because of first blood, injury or death, it was enough to have merely stood your ground, even if both shots missed - which they frequently did.
A pistol duellist might also deliberately miss if they did not wish to harm their opponent (depending on the pre-arranged rules of the engagement), an option not normally available to the sword fighter. Pistol duels became more a test of courage than anything else.
When it comes to dirty tricks, there's little you can do on the day that's not already part of hand-to-hand combat already - assuming you don't try to bring hidden weapons or armour, or have one weapon knobbled. With pistols this becomes even more difficult.
The best time to play a trick is prior to the duel. Have your second boast of how many men you've already killed to intimidate the opponent into apologising; get your opponent incapacitatingly drunk on the previous evening; have him killed or injured prior to the duel by poisoning his meal or hiring a mob of thugs to ambush him on the street; and so on.
So when considering the whole issue of duelling, the main thing to remember is that other then available weapon technology, almost anything goes. It all depends on what both sides agree to before the duel is fought!
