"Cyber Twin Dragon": Its ATK will be 5600, and it can attack twice, allowing yourself to do potentially over 10,000 points of damage at the risk of losing 2800 Life Points—which is avoidable and relatively low, especially considering the potential damage.
"UFOroid Fighter": Use "Gate Guardian" along with "UFOroid" to give "UFOroid Fighter" 9900 ATK. For those who focus on extremely high ATK, "Rainbow Neos" is the ideal monster for this strategy, as its field-clearing effect can be used first before Fusion Summoning "UFOroid Fighter".
"Chimeratech Rampage Dragon": Having 4200 ATK and potentially dealing over 12,000 damage, destroying Spells and Traps that can easily get in the way and being able to attack up to 3 times without any drawbacks makes this one of, if not the, best option for this card.
"Chaos Ancient Gear Giant": Similar to "Ultimate Ancient Gear Golem", it will have an ATK of 9000, and your opponent cannot activate monster effects during the Battle Phase while this card is on the field. Furthermore, its piercing effect is more devastating because it can attack once each for every monster your opponent controls, and it cannot be affected by Spell/Trap effects.