Portal

For this one you can get it done close to the very end of the game in the giant room with a muddy trench at the bottom. Once you get all the way up to the top you can put a portal on the slanted platform directly below you, and one on the top one across from you. If you line it up correctly you'll fly through a few times and get the achievement to pop up. The link to the portion of the video where this is covered is here.