MGS3 features a lot of advanced movement techniques that are not present in the prior games. The basis of which leaves it open for a lot of cool and fun strats, often described as “looking like a speedrun”. While some of the speedtech is difficult to pull off, it is generally easy to learn and the majority of these mechanics will form the basis of any sucessful speedrun.
Quick Headshot
The quick headshot is the most fundemental and most commonly used trick in the run. The basics of the quick headshot are being on the same level of terrain as your target, so that your height matches. Aim at them, go into first person (FPV) and hold the triggers (L2 and R2 on PS) and you will stand up higher so your aim is directly on their head. A clip is below.
(attach video later)
Bump Roll
Snake's roll has a large hitbox, which is as commonly abused as the quick headshot. The basics of performing the action, is bumping an enemy then rolling after you take a few steps forward. It allows you to distract someone and then knock them down to an avoid an alert. It's most common use is before entering a loadzone or to cause a caution in areas such as the warehouse.
Angled Roll
While rolling, you have some level of control over Snake during the roll. You can turn him sharply left or right, which can be used to roll into someone or roll towards a set of stairs etc and turn to continue moving without stopping. It's an essential trick to learn, but it's fairly easy to get a grasp on.
Rail Roll
You can abuse the roll to get over railings and onto the bridge in Dolivdono. It's one of the more difficult tricks to pull of because the game never intended for you to do this. You save a bunch of time using this trick over a hanging drop and in some rooms it's essential to get through as fast as possible. It is also the basis for any warehouse strat for European Extreme. Practice this strat a lot. You'll need it!
Box Rise
Similar to MGS2's Coolant Rise, when you are going from prone to standing, you can cancel the animation by equipping your box and unequipping. Not a commonly used strat, but it can save a bit of time if you choose to use it.
3rd Person Headshot
This is probably the most difficult trick due to the timing being incredibly tight. The only use I've found is against Scientists, when one of them notices Snake, they bend down to inspect you closer. If you shoot right at the time, you can land a headshot.
Box Headshot
Another hard to pull off trick, when you exit a box after an enemy has noticed you and shoot right away, you'll land a headshot due to your position and theirs. A video showing off the strat is below, and worth studying. The strat is easier with the 3rd person camera.
Footstep Silence
MGS3 was the first game in the series to introduce enemies hearing your footsteps regardless of terrain. Fortunately, we can cancel the sound entirely by using grenades. While running, hold your weapon button to “cook” a grenade. It will cancel out the sound your footsteps make, and due to the way grenades function in MGS3, by not “counting down” or “cooking” till you throw them, you can keep the grenade cocked as long as needed, and simply put it away by tapping R2. The most notable use of this strat is Dremuchiji during Operation Snake Eater & The End boss fight.
Box Run
Another new feature of MGS3 was the addition of slopes and inclines. Due to the outdoor setting, you’ll encounter a lot of steep or small inclines and hills, as well as stairs. However, due to how Snake moves while in the cardboard box, you can cancel out the “stutter step” animation that comes with running upward on a slope or stairs. It concretes the box as an essential item in MGS3. The same strat is used in Portable Ops too. However, be careful, as some rooms require you to be slowed down by inclines and slopes.
Punch/Combo Cancel
A straightforward animation cancel, when punching or chaining a PPK combo, snap an weapon on and off to cancel the animation saving a few frames. The animation of holding the gun/grenade etc, overrides the punching animation. A minor trick, but easy to learn and it’s basically free timesave.
Vent Clip
Similar to MGS1, MGS3 features a method of clipping out of bounds by having Snake stand up from the entrance of a vent. This trick is only suggested for advanced runners as it is unlikely to save time as of current, but several places where vent clip can be used for potential timesaves are known. Simply put Snake's back to a vent, lay down, tap the d-pad a few times to put Snake inside the vent but without entering first person or preventing him from standing up. Snake must be able to stand up or the clip will fail. Enter first person manually, turn left about 45 degrees, so it seems snakes head is against the wall, and lean left, then while holding lean, hold X to stand up. Snake will visibly shift backwards and stand up, now out of bounds.