The Web Slinger is a grappling hook that can be found in chests in the Spider Nest Underground biome. It can shoot out and use eight arms at one time, which is currently the highest of all of the grappling hooks.
The Web Slinger has a slightly shorter firing range than other grappling hooks to balance it's increased number of arms, keep this in mind if you are used to the range of other grappling hooks
The Web Slinger has the advantages of both the Ivy Whip and the Dual Hook, at the price of shorter range. It can shoot out multiple hooks and suspend the player in place (like the Ivy Whip), and the player is also able to shoot out all hooks before any land on a surface (the Ivy Whip has to wait for a hook to latch on a surface where as the dual hook can do this but can not suspend between both hooks).
The Web Slinger is a reference to Marvel's "Spiderman" superhero, The Web Slinger bears a resemblance to his web shooters as well.
The Web Slinger has a range of 16 blocks, compared to the Ivy Whip's 26, the Dual Hook's 29, and the normal Grappling Hook's 20.
If you shoot out all 8 of The Web Slinger's webs and then switch to the Ivy Whip, you will get 8 arms on the Ivy Whip (at it's full length) until you jump to break the grapple. This actually goes for any amount of web grapples used after the number 3.
If you use the webslinger to enter a 2 wide gap then keep spamming the E button while attempting to mine straight up (either with the right or left side) you can enter a 1 wide gap and mine vertically.
As with all the hooks grappling onto a door and opening it sends you hurling forward with great speed.