PCS (Power Crouch Stab)
PCS is done usually with a Deku Stick and it requires a Deku Shield (Child) or Hylian/Mirror Shield (Adult).
Perform a Jumpslash, then crouch stab.
Link's crouch stab takes on the last Damage Value, so if you used a Deku Stick for the jumpslash - You'll do Deku Stick Jumpslash Damage, which is 2, with the crouch stab. As Adult, simply just Jumpslash with the Master Sword then crouch stab to get the same Damage Value as a Deku Stick Jumpslash, because Master Sword has the same Damage Table.
PCS is classified as Glitchless.
Pull out Deku Stick and light it off a torch - Then put the burning Deku Stick away but make sure it passes through the torch during the animation. Now you have Flame Storage. When you leave the loading zone it goes away, so be wary of your surroundings when doing this trick.
WESS (Water Extended Superslide)
There are many uses for WESS's in OOT Speedrunning. A WESS is performed by holding ESS out of water-recoil (This can be a crouch stab, Jumpslash, or Mega-Flip / Mega-Sidehop); The most notable places for performing a WESS is: Zora's River Entrance to Kakariko / Market, Kakariko to Kokiri Forest, and above Water Temple in Lake Hylia (Before the Lake is filled).
Torch Flip (Deku Tree)
With this trick you can light a Deku Stick off one of the raised torches in Deku Tree with a Backflip / Jumpslash combo. The most common use for this trick is in Defeat Ganon (No SRM).