Double X costs are typically yucky. But, on a one-drop creature, it’s not a bad ability. Say you wanted to destroy a two-drop artifact: it would cost you 5 mana to destroy that artifact. While that’s quite a bit of a mana investment to destroy one card, on a one-drop creature, it’s not bad at all. Unlike a lot of artifact removal that either is one use or requires a sacrifice of itself, you can keep this guy around.
Even though there are far superior ways to destroy artifacts in Red in most formats, this guy is particularly good in Pauper. That's because in an all-common format, your options for artifact removal are much more limited. You're often only going to be destroying one or two mana artifacts anyway. While it seems a bit inefficient, it's worth playing, since this is a repeatable ability. You can also play him on turn one, and since he's a creature, he doesn't slow down aggressive decks.
Many competitive Pauper decks, such as Izzet Delver, Kuldotha Boros, and Tron play a couple copies of Gorilla Shaman in their sideboards to make certain matchups easier. Gorilla Shaman is worth a look in the right Pauper deck as a tool to destroy pesky artifacts. Reusable removal is always worth something.
For most decks, though, the Shaman one to pass on – although it wasn’t bad in Ice Age Block Constructed. Still, it's a valuable card due to its playability in Pauper. It's also especially good in Pauper Commander (PDH) if you're playing any kind of Red deck.
Have you ever played Gorilla Shaman?