I subscribe to the classic ten essentials:
First aid kit: AMK 0.3 kit with added meds and larger compresses, Uncle Bills tweezers
Lighting: Fenix HL21 headlamp and Olight i2 flashlight, both using single AA batteries
Fire starting: mini bic lighter (daily use), Exotac firesteel, K&M match case with UCO storm matches and built-in mini compass, Bison Designs "spy capsule" with Tinder Quick tabs
Knife: 3.5" folder like a Benchmade Griptilian or SAK One Hand Trekker, plus SAK Classic
Compass: Suunto MC-2G with mirror (and maps)
Signalling: whistle, compass mirror, flashlight, firesteel
Sunglasses: Native Dash XP
Rain gear: poncho or jacket, pants
Spare clothing: gloves, beanie, top insulation layer, windshirt, bandana, spare socks
Repair and improvising: braided nylon line, light wire, "hotel freebie" sewing kit, single use super glue, duct tape
Water bottle: Nalgene Oasis canteen or recycled water bottles
Water treatment: Sawyer Mini and Micro Pur tablets for backup
Shelter: AMK Heatsheets Bivy
Sunscreen, small vial
Spare food: granola bars, hard candy
Insect repellent: DEET, small vial
Backup plan: notifying a trusted person where I am going and establishing a contact deadline.