I've dived with Nurse, Lemon, Bull, White-tip, Black-tip, and a beautiful 14ft Tiger in Fiji all on normal Open water dives in just 2 weeks.
Shark diving with great white's when you know their coming and your in a cage is one thing but being on a normal wall drift dive and seeing everything, including the 2 bull sharks, disappear in a matter of seconds and watching a giant Tiger pull in unexpectedly is one hell of a rush that no one should miss out on. Pretty sure I crappy a little though. And in Fiji I never had more then 5 other divers with me which is really nice if you have dived in some of the crowded hotspots.
Dive Fiji... highly recommended. And the shark dive at Aqua-Trek 3D is fantastic as well, never disappoints.