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.
Default Setting Syndrome: Don't expect any player at the arcade to use anything other than the default weapon, costume, and mission level. Ever. If you're lucky, you might see someone change their weapon or costume. This gets worse when GHOST Squad Evolution is involved; most players don't bother to poke around with the weapon, costume, or level settings, making the upgrade largely pointless.
Demonic Spiders: Knife Mooks in higher levels, due to the increased reaction time required. It's easy if you know beforehand, but still.
Fridge Logic: You Are Ghost Squad! Leave No Traces Behind! (Warranty note: Extensive casualties, environmental damage, and even several EXPLODING vehicles do not count as a trace).
Game Breaker: The TR14 and SPR11, for their ludicrous penetration that makes killing enemies a cinch. Potentially also the CPG7 Uzi Sub-Machinegun, which, while having a lesser amount of ammo, has a quicker reload time and an equally powerful penetration rating.
Polished Port: The Wii release, though lacking the 60 frames per second of the arcade original, is superior to the arcade version due to the option of having a reticle or not, online leaderboards (until the Wii online service went out) , more difficulty levels compared to the arcade original, a training mode, being able to level up your profile without needing a card, and even multiplayer modes for up to four players.