'Recon' Bob Yewlaiter is a character in Stick RPG 2 that will upgrade your sledgehammer if you have the proper materials. He is found at the 24 Hour Laundromat on the first island.
If the player obtains the Unobtainium, or Einsteinium, alongside the Old Weathered Sledgehammer, he will offer to improve it.
The Weathered Sledgehammer will be upgraded to a heavy sledgehammer the first time it is improved. the second time, it will be upgraded to be a Super Sledge