The Shark takes full size 10th scale servo's so take your pick! But most people use the following:
Cheap but excellent
Hitec HS-82MG
More expensive faster servo's
Futaba 9602
Futaba 9650
Futaba 9551
KO 2123
You also want a XRay M18 servo saver. It's the best micro servo saver on the planet!
http://www.teamxray.co.uk/productdet...382500-m18.php