You haven't tried hard enough.
If 12 shots ranging from whiskey, rum, bourbon, vodka, ect. including absinthe (sadly nontraditional) 2-3 minute spans from each other doesn't do it, I don't know what will.
My friend gave up after #9, had a horrible hangover the next morning.
Was quite fun not being able to walk, to say the least. Giggled like an idiot the whole night.