Bored by your .338 Lapua? .585 Nyati just not making enough *BANG!* anymore? Everybody and their brother in your neighborhood has a .50 BMG rifle?
The solution is simple: Spend the dough for the $200 Destructive Device tax stamp and get a 20mm rifle!
What's it good for? Hell if I know; probably useless for anything except turning money into noise, but that's never stopped me from dropping a wad of cash at the fireworks store.
(H/T to the AtomicNerds.)