Some are more jokie-joke than others, but here's my list. Which ones sound good and which ones sound bad?

Death metal + Nu metal = Faygo
Metalcore + Easycore = Alkali metal Transition metal
Pirate metal + Post-grunge = Swashbuckler (My personal favorite!)
Rapcore + Hard rock = Hard rap (Kinda like Lenken Purk's first two albums)
Symphonic metal + orchestra = Mozart metal
Brutal death metal + Extreme grind = Not even music lel
Nintendocore + Pop-punk = Neckbeardcore
Alternative metal + Christian folk = Skillet

I don't know. I felt like doing this and you can't stop me.

Mozart metal sounds nifty, but tough to do right.

Watch this video. It has the same concept.

5066910 That video's why I decided to make up my own genres.

5067380
Oh really. Cool