What's this black box?

Solution 1:

It's an eye crate/Hardstone block. It is impervious to everything (don't waste ammo) save for:

1.Airstrikes (from strobes) Make sure to not miss with the strobe, stand far away and throw.

2.Airdrops (use the Flare Gun next to the Block)

3.The Sledgehammer from the bunker in the Alternate Barn. Smack it a few times and it will open. (You can also use the Stone Hammer, but that's event-only)

It drops: Upon breakage, you can find one round of .45 ACP , Peacemaker , AWM-S , USAS-12 , M9 , 9mm , M4A1-S, BAR M1918, M249, PKP Pecheneg or Flare Gun(each weapon also has ammo along with it). You can find one inside the Eye Bunker in Woods Mode, behind the stone wall, and multiple others randomly scattered around the map in every map. (suriv.io wiki). If it drops a gun, it drops ammo as well.

Hope I helped.