Gear is part of the fun
Some of us enjoy a living off the land with nothing more than a stick, however I think most of us consider gadgets part of the adventure. Whether it's a GPS to find out where you're going or a sophisticated self regulating head to see at night, to me adventure includes gear.
Here some gear I consider essential
No matter what the activity I think having a GPS, map and compass is all part of the fun. While navigation can easily be done with just a compass and map alone, logging and tracking your trip with a GPS and reviewing it later is really cool. A GPS also doubles as a sanity check when you think you might be getting off track.
Against the elements
There's no doubt comfortable and practical clothing makes a good adventure. Part of any adventure should be comfortable footwear, high quality sunglasses and breathable fabrics. A good sleeping bag makes all the difference too hot is no good, too cold is no good, put some thought into a style that would suit your body.
Let there be light
Obviously a headlamp is a core part of night time adventure however so is an emergency wind up flashlight. If you're out longer than expected batteries can die suddenly especially in the cold. A wind up torch provides a good emergency option and could save lives. Also, you should practice making a fire and have the means to easily make one. The best way is to use a flint-like device that throws sparks.
Getting into trouble
An essential part of any outdoor gear should be a small personal first aid kit. It's best if you create your own so you know what's in there. Keep note of what you use as you use it so it can be easily replenished.
Multi-tool and Repair Kit
Without a doubt, a swiss army knife or leatherman-style multi-tool is essential for outdoor adventure. When heading out for longer than a few days you need to be able to repair your gear. Carry a small roll of duct tape, as the Mythbusters will tell you, you can do almost anything with this stuff. This will help you patch up broken gear.
Hydration and sustenance
When you go outdoors it's important to bring water and food with you. Carrying water is a balancing act between weight and volume. Carry a highly portable water filter and you'll be able to turn most water supplies into drinkable water.
While there is an infinite number of recipes for hiking meals, quick-to-hydrate, freeze-dried vegetables and meats are becoming very popular. These can be prepared in the pack in 10 minutes with the addition of boiling water.