LEGO Great White Shark (and Aquaman too!)
Why LEGO didn't package these two together is beyond me. In fact, I'm tempted to create a mini box for these two recreating the classic MEGO Aquaman vs. the Great White Shark set.
According to Brickipedia, this large shark has only appeared in two sets since his debut: LEGO Agents Speedboat Rescue in 2008 and Brickbeard's Bounty in 2009. Suffice it to say due to these limited and long ago releases, the large LEGO shark goes for around 25 bucks or more on the secondary market. Which is why I didn't own him until this past weekend, when I found him at the flea market for a dollar. Pro tip: sometimes it pays to look in those baggies and bins of cheap McDonald's toys. In fact, if you want something for less than expected prices those are the best places to look, because that's where a seller will toss all the stuff they assume is worthless. Truth be told I almost didn't take my own advice, and only found this guy because I made a second run-through that day.
I have now amassed an impressive undersea army for Aquaman to command, including the sawfish, a white Great White, an octopus and a crab. Evil-doers beware!
Not only that, but you can completely close his mouth while the minifigure is inside.
Literal HOURS of fun right there, boys and girls. Hours of fun.