Bike ride down the steepest hill you can find
Go on a Long Distance Bike Tour
Bodysurfing
Build a raft like Tom Sawyer and float down the river
Build or fly an ultra light
Canoe at dawn
Canyoneering
Dune buggy riding
Feel the wind with a naked bungee jump
Fencing (the sport, not the act of building one)
Fly a kite attached to your bike 
Get a tattoo
Give someone a piggyback ride or vice versa
Abseilling ( controled descent down a rope)
Coasteering
Disc Golf
Archery / Cross bow Shooting
Parakarting (Karting with a Parasail)
Go for a Zipline Ride
Go shop at REI for some cool adventure clothing or accessories
Get your pilots licence
Go four-wheel driving
Go hang gliding
Go Freerunning
Make a rope swing
Get your pilots licence
Go to a nude beach
Go to your local scuba diving shop and learn how to dive, go for a dive in the first water you can find
Heli-hiking, Heli-skiing, Heli-anything
Hot-air balloon ride
Go for a Float Plane Ride
Ice Climbing
Kayaking
Kite Surfing
Land luge
Long Boarding
Learn how to use a compass then go and use your skills
Make a boat and see if it floats with you in it
Mountain biking - Cross Country or Downhill
Paintball
Paragliding
Play Frisbee at night
Play underwater hockey
Practice stilt walking
Ride a horse bareback
Ride a horse on the beach
Ride a tandem bike
Rock climbing 0
Sandboarding (snowboarding on sand)
Sea kayaking
Ski/golf/sail all in one day
Skydiving
Try to break a world record
Unicycle
Wakeboarding
Waterskiing
Windsurfing
Whitewater canoeing
Whitewater rafting
For extra fun shivers - combine 1, 2, 3 or even 4 of these activities in a day.
If you have no energy- go get the latest swimsuit issue of Sports Illustrated and pretend to be getting fit.
Grand Adventures