The ability to capture ghast fireballs and redirect them back at the ghast without them exploding in your face. Right now you can capture them, but they maintain their velocity, meaning they will be constantly trying to go one direction. If you are in that direction, kaboom. If you fire it with the gravity gun, it goes in the direction you fired for a little bit, then arcs and returns to the direction it was fired at. Using the gravity gun to redirect the fireballs gives a similar effect, arcing where you were looking, then returning in the direction it was trying to go.
(Could be a feature for the charged gun. Remember the Half-life 2 energy balls?)
So, if this mod is now in use, will the Portal Gun lose its ability to pick up blocks to balance out the use with this mod? Otherwise, why would I build this if my Portal Gun can do the same? Also, we need this in Sphax's Texture Pack and Faithful.