These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Alternate Character Interpretation: In the second game, the Mercenaries honestly don't care about whoever wins or dies, just whoever pays best. And given how much money Solano had in his coffers, one can't help but wonder if the Merc would've sided with Solano had he not attempted to pull a double cross...
It's practically stated right in the manual they don't care who's right or wrong, just who pays; hence they can work for everyone from freedom fighters to gangsters.
Artificial Stupidity: In the first game, planting C4 on the back of an occupied vehicle will cause the driver to go straight forward in an attempt to get away from it. There's one place in Haeju where you can do this causing the vehicle to drive straight off the end of the dock. note It's easiest to do this with civilian cars
Critical Research Failure: Mattias' backstory, as written, is impossible. Both when the first game was released and when Nilsson's service in the Swedish Army was supposed to have happened, Sweden did not have a professional army and you definitely couldn't join the army at 17. The Swedish army at the time conscripted its recruits at age 18 or after high-school, and the only career soldiers were officers. None of this information would have been impossible to find with a quick internet search. Also, someone with Nilsson's history would most likely have been declared mentally unfit.
Demonic Spiders: Tanks. You will rarely get off a shot before they hit you, and if you're in a vehicle, the rocky terrain causes your reticule to bounce all over the place.
Ear Worm: The original game's title theme, and "Oh no you didn't!" The second game also has a low-key, acoustic guitar version of the first game's theme playing in the background while wandering around Venezuela, which really gets into your head.
Sequelitis: World In Flames isn't regarded as a bad game, but it is criticized for not bringing enough new aspects to the table. More of an issue occurs with the plot, which treats all three mercenaries as acting like Mattias, where in the original they had their own distinct personalities, as well as being a Shallow Parody of The War on Terror with it's underlying message that World War 3 would start in Venezuala just because all the factions wanted to control the oil for profit.
Stop Helping Me!: In the second game, Fiona can approach this, if you decide to wander around aimlessly without really doing anything.
Coming too close to even a friendly faction commander will cause him to negate that disguise, sometimes at inopportune times.
Due to Artificial Stupidity, allied NPC soldiers can become considerably more dangerous to you if they are carrying explosives than the enemy. An Allied Nations soldier on a Mk. 19 or a Chinese Anti-Tank soldier carrying a fuel-air rocket launcher will gladly help you kill the enemy that is two feet in front of your face.
That One Sidequest: The Pirate cargo missions from 2. All of them. Not only are you required to drive a rickety pickup truck laden with various cargo through twisty, uneven roads (the better to make the cargo slosh out) practically infested with hostile vehicles (your truck can take approximately -5 damage before exploding and is easily flipped through collisions and near-miss explosions) and helicopters (see previous parenthetical, add homing missiles) while unarmed, but the majority of the problems would be solved if the player character were simply able to lash a tarp over the truck bed.