Gravity Gun
Note: If you're looking for the other set of guns, check Paint Gun.
Warning DO NOT use more than one of these special guns on a chamber, as their effects will add up.
The Gravity Gun is a set of two items made by Radelite, ENDERZOMBI102, Flash4433, Niin31 and Linking-yellow. It's a portal gun that can't shoot portals. Instead, it pulls props towards the player, or pushes props away from the player, like in Half-Life 2. There's a Gravity Gun MK1 and a Gravity Gun MK2.
Although the Gravity Gun doesn't allow the player to shoot portals (however, autoportals still work), it gives the player a brand new mechanic to play around with. The MK1 pulls and pushes props, as they're always both equipped, but the MK2 can also make props float upwards, however, unlike the MK1, you can only have one power equipped at the time, and the other key switches the gun's operation. MK1 should be used if there are parts of your map where you have to be fast with your inputs, and the MK2 should be used if it's a slow-paced map. Play Half-Life 2 for more ideas.
In the future, the Gravity Gun will have a MK3. It might be a SuperCharged Gravity Gun.