The 3rd Birthday/YMMV


 * Base Breaker: Aya's apparent Chickification. Although the truth is more complicated...
 * High Octane Nightmare Fuel:.
 * It doesn't help either that Aya's expression at the sight of this thing is blank horror...
 * From the soldiers' perspective, the fight with could easily qualify as this. One of the soldiers randomly walks up to him and  starts talking to him for no visible reason. The soldier suddenly raises his gun to shoot, and  Armor Piercing Slaps him to the ground. Right afterwards, he transforms into some kind of half-Twisted monster with disproportionate limbs and tentacles sprouting out of its back. I'd be freaked out...
 * A bit of Fridge Horror here: I'm sure many of us have dived out of a dying soldier - and heard the screams - but what do you think the soldier him/herself went through? If they are conscious when Aya possesses them, that's kinda creepy, but it's worse if they're not. One moment you're in cover, a fellow soldier stumbles for a moment, the next you're squirming on the ground with blood pouring out of every orifice.
 * Nintendo Hard: You can die a few times even during Easy mode.
 * Tear Jerker: The Ending.
 * That One Boss / Wake Up Call Boss: Easily many of them are, depending on how well your DNA board is customized and how well you've kept up with upgrading your weapons.
 * Unfortunate Implications: Graituous shower scene (granted, the second game had one too), fanservicey-costumes that can get torn off enough to see her underwear, an Overdrive system usually involving Aya to take possession of a male soldier in order to defend herself...
 * Even more so
 * The Woobie: Eve. The poor kid is in dire need of a hug.