These TCG rulings were issued by Upper Deck Entertainment and have since been deemed unofficial by Konami. They were previously considered official and can still be correct, as long as they follow the official gameplay rules, or unless Konami has issued a ruling that says otherwise. References: 
Fusion Devourer: If this card battles a Fusion Monster that is equipped with "Axe of Despair", etc. that Fusion Monster's ATK will be 0 for Damage Calculation.
Gradius' Option: The ATK/DEF of "Gradius' Option" is the same as the current ATK/DEF of the selected "Gradius", not the original ATK/DEF. So if you equip "Axe of Despair" to "Gradius", the ATK of "Gradius' Option" will also increase by 1000 points.
Gradius' Option: Equipping "Axe of Despair" to "Gradius' Option" has no purpose. Activating "Reinforcements" targeting "Gradius' Option" serves no purpose. "Luminous Spark" on the field will not change the ATK/DEF of "Gradius' Option". It always has the same ATK/DEF of the selected "Gradius".
Pole Position: The opponent has "Blue-Eyes White Dragon" (3000 ATK) and "Pole Position" face-up on the field. I have "Gemini Elf" (1900 ATK), and an "Opticlops" (1800 ATK) equipped with "Axe of Despair"(+1000 ATK; 2800 total) face-up on the field, and a Set "Ring of Destruction". If I activate "Ring of Destruction" to destroy "Blue-Eyes White Dragon", then "Opticlops" will be the highest ATK monster on the field, and cause an infinite loop (it is the highest, it isn't, it is, it isn't, etc.). Therefore, I cannot target "Blue-Eyes White Dragon" with "Ring of Destruction".
Wild Nature's Release: If "Ojama Yellow" is equipped with "Axe of Despair" (1000 ATK, 1000 DEF), if "Wild Nature's Release" is activated then it increases "Ojama Yellow" to 2000 ATK, 1000 DEF. If "Axe of Despair" is then destroyed, "Ojama Yellow" remains 2000 ATK, 1000 DEF.
Megamorph: When an effect modifies, doubles, or halves the original ATK of a monster, you must apply this first. After calculating this value (the monster's new current ATK), any gains or losses (increases or decreases) to the monster's ATK are applied to the calculated value.
Submarineroid: "Submarineroid" does not assume new "original ATK" values. Its original ATK does not modify after the battle is concluded. It does not become a "new original ATK" or anything of that sort. It's effect means to explain that the battle damage inflicted will be equal to whatever "Submarineroid's" original ATK is. If equipped with "Axe of Despair", it will only inflict 800 damage, and "Submarineroid's" ATK remains at 1800.
↑Konami Judge Program Rulings are considered unverified, as their source(s) are not publicly viewable. They are not confirmed as applicable to the TCG until they have been officially published by Konami.