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.
Game Breaker - Quite a few (for both players and Referees), though some are less obvious than others. Luck, an otherwise useless attribute (despite the official suggestion of how to determine psi abilities), is the source of one of these, as it's possible to get a result of 40~45 on any given skill roll with the proper setup, almost guaranteeing a critical (and possibly even an instant kill) in combat.
A handful of the game breakers can be negated by a watchful referee, especially if they require the players to run all designs by them. The easiest of these to spot are the scaling exploits, in which a munchkin tries to design a game-breaking mekton abusing the scaling rules.
Burst (especially Burst Infinite) can easily become this, if used right. It is quite possible, in Mekton Zeta, to create an energy chainsaw that can quite literally saw a battleship in half, every other turn (using the 'cooldown' turns to close in on a new target) for about a hundred points.
A hundred points being the entire points allocation for a production line "grunt" military mecha. Not to say that the weapon isn't exploitative as hell, just that 100CP is a *lot*.
Reverse Funny Aneurysm: In Operation Rimfire, one of the characters had a girlfriend called Maria who was brainwashed and given an alternate personality. Nearly two decades later, Gundam 00 was made...