-THREE ways to start a fire (strike anywhere matches, flint & steel, cigarette lighter)
-MAP & COMPASS. A GPS is great but IMO it is no substitute for a USGS Quad map when trying to figure out where you are and where you think the elk may be.
-SIGNAL MIRROR & WHISTLE. To help the search party find you...just in case.
-BIVY BAG or EMERGENCY BLANKETS, ROPE or CORD. To set up a primitive shelter if the weather gets bad.
-WATER PURIFICATION. Never drink mountain water unless it is filtered. There are a lot of options but I prefer "Aquamira". It costs $15 and will last you weeks of constant use.
-TOILET PAPER! (self explanatory)
That stuff is mandatory just for SURVIVAL. As far as the Elk hunt itself, add the following:
-cloth game bags (roughly 6 for a decent sized bull elk)
-calls, scents, etc.
Lastly and very important: SUNGLASSES and BRIMMED CAP. I'm not sure which state you are hunting in, but here in Colorado your entire trip will be miserable without these two things.