A simple one: As noted on the Foreign Language Title entry on the main page, the characters for the titular weapon would be, when placed together like they are, more properly read "daitō" rather than "daikatana." However, what better for hiding a weapon than giving it a name with unexpected pronunciation, thus making any written documents actually written in Japanese look like they're talking about something else?
The infamously impractical and sometimes suicidal weapons actually make sense in-universe, at least for the first episode; you're fighting your way through Mishima's own prison facilities and controlled areas where he's already taken over the world. Given how Mishima undoubtedly controls the world's weapon manufacturers, it's highly likely that he has them put new weapons into production without testing for design flaws. Beyond simply cutting corners, it also means that the guns are impractical for the tight spaces of his prisons and factories, making things harder for would-be resistance fighters or disobedient minions. Considering he turns people into burgers, it's right up his alley of dickery. Notably, the other time periods where his control is absent are where weapons get (mostly) more practical, especially in 2030 where you get semi-futuristic guns that are worth a damn right before the point in time Mishima would take over.
As Suspicious points out during his and Proteus' LP of the game, the Athena statue that you see in the final stage of the 2nd world is implied to be the real Athena turned to stone by Medusa. Thus when grabbing the Eye of Zeus, whoever the disembodied voice that calls to you when you grab both it and Poseidon's Trident is kills Athena by destroying her body to clear a path to Medusa, even though killing Medusa could reverse the process.
