first of all I am making a trap from saw and i need spikes to go on the inside. i dont want to spend alot of time on them and i dont want to have actual spikes.

here is the trap-
second, can you buy a "mat" that you step on that turns a light on?

You could get some dowels from Home Depot or Lowes, cut them off to length and sharpen one end. Then paint them to look old, rusty and glue them to the inside of your head trap.

Another more time consuming and but realistic way: Make a rubber/silicon mold of a large nail(s) and then cast the nails with latex. Then paint to your liking.

Yes they have mats that trigger things when stepped on. If you do a search for "trigger mat" or something similar I am sure you will find what you are looking for.

Are they going to be put through much contact? Or are they going to be part of a costume or similar, where they will be seen, and possible touched occasionally, but not regularly pushed on / rubbed / etc...
Depending on how closely someone's going to be able to examine them, perhaps you could use scissors to cut out slivers of foam rubber that are approximately the right size, and just paint those up.

For buying a mat switch:
Check eBay, under "mat switch" - I found a few items there.
There are also some good how-to's on making your own mat switch, if you're on a tight budget.

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i know i saw a mat switch triggered outlet on one of the prop sites i just can't remember which one. i am still trying to find it. and what about great stuff foam spikes

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I think frightprops has the mats.

I don't know if you've ever heard of "electric erasers", but the refills are 7 in. pencil erasers that come in a box of 10 or 12, and I've seen these as cheap as $4.79. Cut these in half, and you'll have 20-24 pieces at 3.5 in. each to work with.

Another idea you might consider is using the glue sticks for hot glue guns. They're pretty cheap, pliable, and paintable too. Good luck!

Good idea on the glue sticks! They even have the smaller diameter glue sticks.