The Extreme Academy at Watergate Bay has a wide range of extreme sports to choose from.  These can be booked in advance if requested.  

Lusty Glaze at Newquay also has a zip wire, and offers more adrenaline sports.

Spheremania for zorbing is nr Newquay, as is Newquay Paintball.

St Eval Kart Circuit is a only a few minutes away.

Padstow Sealife Safaris offer Coastal trips by powerboat.

Go! Indoor Karting and Laser Quest at Plymouth.

The ATV Centre at Blackwater has three circuits for Quad biking.

Adrenaline Quarry at Liskeard is great for Coasteering and Zip Wire.

There are also other activity centres in Devon & Cornwall, with rapids and zip wires.

Oh, and surfing ... that goes on here a little bit! At Watergate, both Extreme Academy and Gone Feral will sort you out with some equipment.  There's also Kingsurf at Mawgan Porth, Harlyn Surf School and Kayak Hire, and loads of places at Fistral and in Newquay Town.