I think there's a hierarchy in pitch priorities:

1. Clarity.

2. Brevity.

3. Uniqueness of product.

4. Uniqueness of pitch.

...and so on. If you can make your pitch more unique with humor in a way that doesn't cross any boundaries of taste (and if what you intend to be funny is ACTUALLY funny), then go for it!

For example, I saw a pitch to a room of startups, VC, and press that involved singing, dancing, weird accents, and a ukelele. I loved it and remembered the company's name, the product, the founder, the works. Because of that pitch (and their general attitude toward the tech ecosystem), that company's getting a video interview and a shot at a guest post on RWW.com.