Alrighty, this is for WasteOfGoodSuffering. I will try and tackle the slit throat effect... I know this will work, but don't have pictures to show step by step instructions so bare with me.
INGREDIENTS:* Get yourself a nasal aspirator (this is also known as a "baby snot vac"... mostly by me)

* Get a thin straw preferably from this kind of style juice box

* Superglue

* Foam Board

* Glue Gun

* Cardboard
(image not necessary I hope)
* Gaffer tape
(Or any black tape or duct tape painted)
INSTRUCTIONS:> Drink your kool-aid jammer and super glue the straw to the baby snot vac. (so it sticks out of the snot vac):

> Draw a blade shape on the foam board and cut it out
> Take blade shape and trace it onto foam board again (making a copy)
> Cut out the copy and glue the two foam blades onto the straw (have the straw about half way from the top of the blade and the bottom)

> Tape the straw with scotch tape... like so (the gap is to allow the blood to flow out (you can use less tape if you want the blood to come out somewhere else... but make sure it's still near the end of the straw):

NOTE:
At the top of the blade, use the glue gun to keep the top together... so the bottom of the blade is taped, and the top is glued.
> Take some card board and cut two rectangles, then put them on either side of the bulb... this will be your handle.

> Take the black tape and wrap it around the cardboard to make it look like a handle

> Paint the blade a base coat of stone grey and a second coat of metallic silver... this will make it look like a real blade (the tape will make the edge look extra shiny, and extra sharp).
> dip the knife in a cup of fake blood and squeeze the bulb... let the blood suck it...
> run it across your actor's throat while squeezing gently on the bulb (or hard if you want it messy).
> There you go... you have a knife that can now cut peeps!
The cool thing about this is that you can make any neat designs in the foam board... so if you're character needs a medieval style dagger just cut out the foam that way and decorate the handle... the possibilities are endless.
NOTE: Remember to clean your knife after using it, depending on what you use for fake blood it can get moldy. I suggest wiping the blade and sucking up water with the bulb and squeezing it out a couple of times.
Please post any other gore effects that you want me to take a stab at (pun intended) or post your own designs!
When I have some time I'll do a step by step make-up tutorial on how to make the actual slit throat wound using make-up! Also... maybe a burn wound? Iunno... I'll do requests for that too!