Air walk: Press and hold jump, then spam crouch and use anywhere on a ladder. You're not able to jump while air walking so you will have to ascend using sloped ground or objects. to descend repeatedly crouch. To regain the ability to jump, save and load the game then touch the ground.

Object boosting : Most decorative objects are solid, meaning you can stand and jump off of them. By using explosives or firing at them while having slow-motion activated, you'll be able to boost yourself vertically. However, if the object is moving too fast then you won't be able to jump on it, you'll just clip through. This means that most smaller objects are not suitable since their weight is so light, meaning they will traverse much quicker than for example cardboard boxes or trash cans. To counteract this you can move the object further away from the centre of the explosion thus giving it less velocity.

Crouch glitch: You can move at running speed in areas where you normally only can fit by crouching (like vent shafts). Bind crouch to the scroll-wheel and run up to the place you want to crouch through, then scroll one step with the scroll-wheel while holding forward and you'll be in crouch glitch mode until you stand up again or crouch longer then a few frames.

Melee cancel: You can cancel out the punching animation by crouching after the attack, therefore being able to perform multiple punches in a very short time span.

Human boost: Normally you're only able to stand on people's heads without being able to jump from them. A way around that is to first glitch into them by simply walking at the right angle, then spamming jump. At some point the game throws you out of the person you glitched into with a full jump.

Pillar climbing: You can climb certain types of pillars, walk towards the pillars edge and spam jump, with the right angle you should gain vertical height. It is important to not press any directional keys until you are at the apex of the climb, where you should turn the character towards the ledge you want to climb onto while pressing forward, slowmo helps preforming the glitch correctly. The climbing speed is also related to frame rate, some walls are climbed faster on high fps while others are climbed faster on low. Freescroll helps while climbing walls that are affected negatively (slower ascend) by high frame rate.

Corner clipping: You can clip into most objects which have non-blocked corners. Stand on one of the corners and start spamming crouch. If you positioned yourself correctly, you should fall through the object. Now jump and crouch repeatedly towards the object and with some luck you'll be able to move freely within the object. If you simply start running around after just spamming crouch at the corner, you'll get ejected. Also note that the object must be tall enough to be able to jump crouch into it.

Credit goes to: https://kb.speeddemosarchive.com/F.E.A.R.