My favorites:

**Proof by cosmology**

The negation of the proposition is unimaginable or meaningless. Popular for proofs of the existence of God.

**Proof by semantic shift**

Some standard but inconvenient definitions are changed for the statement of the result.

**Proof by religious belief**

God told us that X is true

**Proof by parent**

"Because I said so."

**Proof by slippery definitions**

The definitions are not so well-defined that the reader can tell exactly what they mean.

**Proof by eminent authority**

“I saw

in the elevator and he said it was probably NP-complete.”Karp

David Karp?