Bad Ass: Many characters are statted to be in line with their fictional counterparts. Lu Bu is a demon on horseback and in later games, when dueling is brought into the series, can easily defeat an enemy general in one hit.
Chewbacca Defense: In XI, using the Sophistry option would have your officer throw in a ridiculous, silly statement that gives the opposing officer damage and leaving them confused on what your officer just say. Oh and randomly changes topic.
Combination Attack: In IX, when two compatible generals are paired into the same unit, they sometimes both trigger an special attack at the same time, causing more casualties to the enemy forces.
In XI, this doesn't happen if the two compatible leaders are in the same unit, but if they're each leading a different unit within attacking range of the same enemy unit. There's a chance that attacking with one will cause the other's unit to run in and do some damage as well, without using up the unit's attack for the turn.
Continuity Nod: Nobunaga's Ambition (a similar game set in Japan) characters have their portraits available to you in the Create an Officer mode if you beat the game in some versions.
Other warlords from other periods in China's history are also playable.
Defeat Means Friendship: In XI, your subordinate officers often find free officers in their towns and ask them to join your force. A duel is suggested to see if you're worthy of their services. If you win, those officers join your army, even if you purposefully wounded them numerous times during the duel.
Some officers have to be recruited this way, although in some rarer cases, a debate is used instead of a duel.
Downer Ending: If you did poorly on your way to uniting China and choose your strategists and heir equally poorly in some later games, it turns out that your empire may not last as long as you would have hoped.
If you play a vassal and unite China in the name of your lord, you may wind up being executed because the lord fears your great ability if you have a poor relationship with him.
Easy Logistics: Especially in the later games, quite well averted. In XI, for instance, you need to take food along with your army on trips, and occasionally gold, if you intend to rest your troops somewhere, to pay your officers. If you don't do the former, then your army will slowly starve to death, and if you don't do the later, officers will lose loyalty.
Kill It with Fire: XI allows you to build fireballs that can damage multiple units in a line, as well as multiple structures when fully upgraded.
In X, units require high morale to move quickly and will retreat if their will is depleted.
In XI, unit morale is used for special attacks.
Plot Armor: In X, as long as the story is still relatively on track, some forces (namely, Liu Bei) get attacked very infrequently, compared to how weak their cities are. Reinforced by the fact that, the minute the plot goes off track, they are instantly steamrolled by another force (namely, Cao Cao).
RPG Elements: VII, VIII and X are all from the viewpoint of one officer whom you control. Other games in the series allow skill point upgrades as well.
Video Game Cruelty Potential: In later games, when you capture the last city held by an enemy force, you capture every single officer in that city; sometimes it can be over 30. You can put them all under the sword. Some officers take the news of their upcoming deaths in dignity; others don't.
Video Game Long Runners: The first game came out for MS-DOS, NES and other systems in 1985, and has run on for over 11 games in 21 years.