Two times at Molokini I've sighted big guys out at the limit of visibility. In one case I'm pretty sure it was a tiger shark. In the other case, on the following morning the diveop B&B had a great white go cruising by the group. A Captain/DM off of another dive op, Mike Severns, has some superb video footage of a tiger munching on a manta that got tangled up in a mooring line on the Enennui side of Molokini crater. While chewing after ripping out a hunk of the dead manta, the tiger shark would cruise over to check out Andy, who was trying to keep a rock between him and the shark.
About 1/2 of all shark fatalities in Hawaii are on Maui.
The facts of life, though, is that you will see lots, and lots, and lots of whitetip reef sharks (who vye with nurse sharks for the title of pussycats of the ocean).
Molokini has a point where grey sharks commonly school. In the rare conditions that allow trips to Molokai, hammerhead sharks are often spotted. I don't know of any place where tigers are routinely sighted, but if you look at reports of shark attacks, the most common places are between Kamaole1 and Makena Landing in S. Maui, and in West Maui at Olowalu (MM14) and from Kaanapali north/northwest a few miles. Luckily, sharks seem to prefer swimmers and surfers that are on the surface over live scuba divers. One dawn in March I watched a dorsal fin cruise back and forth just offshore of Kam3 beach, at one time getting to about 50 yards distance from someone out for their morning swim. The tiger? didn't seem to have any interest in the swimmer, but instead repeatedly swam past a spot where I've seen both a cleaning station and turtles hangout spot.
If Shaka Doug doesn't jump in to this thread, he'd be a good guy to PM as he does shore dives in S. Maui almost every day.