The rules have changed over the years. Sometimes they get two items, sometimes three. I may have even seen four. They always get a knife of some sort. Sometimes they get a fire starter, sometimes a dumbass prefers a fire making kit, sometimes neither. I've seen a pot to boil water as a chosen item, or as a provided freebie.
Assuming a knife and fire starter are provided, the choices are usually one of the following:
pot to boil water
mosquito net
fishing net
fishing kit (line and hooks)
fishing spear with or without mask
cordage
My choice would depend on the location. Is there a way to purify water without needing a pot? How bad are the bugs? Is fishing likely to be a worthwhile activity, and is it limited to the ocean? What are the other protein/food options?
I generally like the thought of a mosquito net which can serve dual purposes, but only if potable water is secured, and only if bugs are really bad. They did not have one on the last XL, and did not seem to miss it. It likely would not have helped at all with centipedes and scorpions.