At the height of the Napster controversy, the folks at Camp Chaos created a series of flash animations featuring Metallica's Lars Ulrich and James Hetfield. James, aside from being a caveman mentally, was also terrified of fire. So naturally, in their Celebrity "Who Wants to Be a Millionaire?" parody, he gets lit on fire.
Probably alluding to the fact that Hetfield was badly burned by stage pyrotechnics during Metallica's 1992 tour with Guns N' Roses, thus proving that no matter how much they called Metallica a bunch of dicks, their detractors could still out-dick them rather easily.
Flying (aviophobia) or Heights (acrophobia)
In Red vs. Blue, one of The Meta's only weaknesses is that he's afraid of heights. His death is appropriately ironic; he's knocked off a cliff into the ocean.