My gear collection aside, here's my hand-picked bare essentials.
-Doug Ritter's Kit, with home-made first aid kit, but the ultralight works.
-Multi-tool with saw. The blade is a back-up. I prefer Leatherman, but the SAKs are cheaper with good build and features, never doubt an SAK.
-Reliable folder as a minimum, fixed blade if possible. I've heard good things about the ultra-bargain Moras.
-Basic shelter material. Those disposable ponchos are junk to me, can get a roll of giant garbage bags for tons less with more material to work with.
-Rain gear. I prefer a mil-spec grometted poncho, doubles as a shelter.
-Any LED light even for a day-hike, LRI Photons are last-ditch back-ups. Any backpacker will suggest a headlamp, so do I, Target sells an Energizer one for ten bucks that features a red LED. That's if you're just preparing, for dedicated use get something you can rely on.
-If feasible, throw in a Bic lighter or two, the Ritter Kit has an excellent fire starter but a lighter is a lighter.
-Larger Nalgene or Camelbak for hydration. Purification tablets are only necessary if you'll be near water or risk an extended stay, they definitely deserve a place in a kit but don't pack them if you're walking through a National Park trail.
-Gloves. Simple as that. Cold weather, handling things in the outdoors, just bring some gloves.
-Fox 40 whistle for every person in the group.
-Bandannas
-Paracord weave such as a bracelet or key fob