Portal Glitch Prevention
Portal Bumping Place Portal Bumpers around cleansers and other such objects so that the player can portal bump past them. This glitch works on Valve's maps. How to fix: Place func_portal_bumpers around the edges of things like cleansers, and a func_noportal_volume as well. http://i258.photobucket.com/albums/hh243/omnicoder/portalbumping.png Portal bumping on the last level of Portal. Portal bumping here allows you to really mess with the game. This is why it is so important to fix this.
Going Behind Portals Avoid 1 unit thick walls. Players can abuse these and get behind them, althogh it is very difficult.
Infinite Loop Watch out if your room has a portalable surface on the floor, with another on a higher section of floor. The player can abuse these to gain momentum. Also watch out for portalable ceiling over portalable floor. Edge Hopping This works on one of Valve's maps. Make sure your metal walls, espically if they are detailed with some blocks sticking out, cannot be traversed. Portal through Portal AKA Portal Standing Ensure the player cannot stand in one Portal, fire a portal somewhere uninteded then quickly step back inside the portal they stood in to end up in an unintended area.
Seal the bottom of Goo Pits! A lot of people ignore this. Seal the bottom of goo pits properly. It doesn't kill instantly. Depending on the layout of your map someone may be able to get outside of or on top of it from here, and reenter later.
Jumping off switches and other things Players can Jump onto switches and railings. Ensure they cannot jump off of these to get somewhere unintended. Example: http://i258.photobucket.com/albums/hh243/omnicoder/flux12.png
In the picture, you can jump from the switch to the ledge with the cube.
Portalable hallways with triggers Ensure that any area the player could get too with a portal therefore avoiding the hallway also has a trigger. Trigger_Look's and You Always have a backup trigger incase the look doesn't get.. looked at. (where applicable) Item climbing Abusing the physics system with Prop_physics objects to climb walls. Not much you can do about this unless you have invisible blocking brushes to block areas the player shouldn't be able to get too yet. Unintended Shields Make sure that turret related areas don't have any unintended shields. If the player has access to a dead turret that could be used to shield, and circumvent part of the map (eg. getting a box) find a place to put a cleanser to kill the turret, or make the turret Fizzle out when dead.