Borderlands 2 gambling vault symbol, sir hammerlock's big game hunt - vault symbols - borderlands 2 wiki guide - ign
Go east from the first assassin Wot's portal to the large backlit fan on the wall, over the pit with the spinning gear. The symbol is on the wall directly to the south. This is a completely normal grenade and will damage any player character in the blast radius, not just the Vault Hunter who actually used the slot machine.
Go over the crates and onto a ledge. After that, you will come across a ramp leading upwards.
You will find the symbol on its door. Live grenades and eleven of the twelve eridium bars from a triple eridium reward will drop to the floor. From here, you need to jump across to the large opening in the sleeping room. From here, you can get to the roof.
In a solo game, a masher tentacle must fling the player up to reach it. From the top step, you will be able to spot the symbol on the wall. Terramorphous Peak Left of the elevator lift near the vending machines. The damage dealt by the grenade is scaled to the level of loot in the machine. All non-pistol weapons from the side drawer.
To the west, across a sheet of ice, there is structure made of sheet metal.
The other is to jump out from the 2nd floor balcony of Crimson Raider HQ and pass through the rooftops to the right. The symbol can be found at its back side. In the middle on the back side of the crate by two ammo boxes. From the location of the previous symbol, you will find a bench on the right side.
If your main concern is taking out enemies and not to explore, you will hardly come across few of these.