For clipping through walls, I either leave it to human stupidity to shove it through the floor or walls, but glass and doors have a trigger in the center that tells the gravity gun to drop the object "held".

I use the commands +use and -use to hold the summoned objects, so that doesn't really becomes an issue. Other than the gun phasing through walls, of course.

Since the topic is Gravity Manipulation, I may as well post this thing I slapped together in a couple days. A working prototype HOVER-BOARD. IT took some doing to find a method that glitched the LEAST, but I found it successful. Just a few Some notes; You have to grab the board like any object. Jump to achieve lift-off, as your feet are still touching the ground and are creating friction. And Looking up elevates you as well looking down descends you. Have fun

Nice, I tried to build a skypad for my Bastion pack once, but I never fully got it working.

I quickly found that parenting triggers that cause movement should not be parented to what they are intended to move. It remained completely immoblie. So I set them to move the player instead. I may probably create a fold-out animation with some func_doors and such to give it a better appearance, But I say i did pretty well

EDIT: Here is the newer version with the animation and refined triggers. Have fun with it.