If given a selection of simple survival gear and an opportunity to take only three items in anticipation of being dropped naked into a temperate forest with water easily available, perhaps near a river or lake, I think it would be: lighter, knife, rain poncho with a liner.

Preferably simple, robust and reliable models of each item.

Thin strips can be ripped from the liner or poncho to get basic footwear and braided into light lines to tie things up with but I would search pretty hard for suitable alternatives (grasses, vines, bark, etcetera) to avoid having to sacrifice my equipment.

Footwear and a means of containing water so it can be boiled would be my next concern. Shelter, followed closely by exploitation of any potential food supplies I may have observed, would be the next concern.

If I got really lucky and there was plentiful, and naive, game I might trap, tip up and dead fall traps are pretty easy to rig but bait is often the biggest impediment, skins might help more permanently solve the water and footwear issues.

A lot depends on the specifics of the area and season. Knife, lighter and poncho with liner would tend to be near the top of most lists and it would, IMHO, be a fair to good choice for a wide variety of locations.