Omnipotence paradox
An omnipotent being is one that can do anything. Can an omnipotent being create a stone that is too heavy for him to lift? If he can, then there is one thing he can't do: lift the stone. If he can't create it, then there is one thing he can't do: create such a stone. Either way, there is something he can't do, which contradicts the assumption that he is omnipotent. This is a paradox.
A similar paradox is the question: what happens when an irresistible force meets an unmovable object? Here, irresistible means it can move anything, and unmovable means nothing can move it.
In both cases, the question is making implicit assertions that are inconsistent and self-contradictory. In the first paradox, the phrase omnipotent being is implicitly stating that any phrase such as a stone too heavy for him to lift is meaningless. In the second paradox, the phrase irresistible force is asserting that there are no unmovable objects for it to meet. The phrase unmovable object is asserting there are no irresistible forces for it to meet.
These paradoxes are similar to the famous question: have you stopped beating your wife yet? When an innocent person is asked this question, the appropriate answer isn't "yes" or "no". The appropriate answer is "your question is implicitly asserting something incorrect".