I had a small kit, based on a metal band-aide box. I had built several over the years, and found one last summer in a pile of my stuff in the barn. It had sat unused so long, the medicine expired in 1994. The Solitaire AAA single cell flashlight had a Energizer battery in it that expired in 95... It still worked! (I use lithium now) For fire I like Bic lighters or Life raft matches. A small Swiss Army Knife, A 10' hank of cotton string. Water purification pills. Mylar blanket. First aid kit (3 or 4 band-aids, 1.5" sq. of mole skin, 2 pack of Tylenol). Sewing kit (2 large safety pins & thread and needle) 4 quarters & $10 bill. I have taken to adding a plastic survival whistle that has a compass, magnifying glass, flint striker and match safe on it. Some kits have a wire saw, some don't.
A couple years ago I saw Cabala's selling kits based on a Qt. water bottle, and have made a number of this type, but the smaller size are left in a coat pocket permanently.
On hatchets; I've gone to used hatchet heads (from yard sales), sharpened and re-handle with a California framer handle (straight) and the butt tapered, they throw like a tomahawk and pound like a hammer. This runs about $15 and 1 hour. Sometimes I make a leather cover that a belt will work with.