Plot hole: The legend of the black knight (in this film) is that he can breathe dragon's fire. Jamal somehow rigs up his aerosol spray-can inside his helmet to shoot out the flames. However, there are three problems with this: one, how did it fit in the helmet? Two, how did he activate the spraying mechanism without his hands? And three, how did he even ignite the spray? (00:49:15 - 01:13:55)
Plot hole: When Jamal saves Knolty's life and is invited into his home, he leaves his work jacket at the lake shore. This jacket is where he kept his spray-paint. However, later in the movie Jamal has somehow recovered his spray-pain.