It depends on where the player is in the game. As for just fun-to-shoot, Viking's spinner is great. But specific instances where center shot is awesome are:
Whitewater for the vacation jackpot. Machine goes apeshit. Awesome.
Destroying the ring on LoTR.
Collecting the final A-Bomb shot on "move your car" in CFTBL.
Cashing in on "do or die" in IM.
Billionaires club shot on BoP.