Inside Cooper Battery (a.k.a. The Tempest) we discovered the Galaga submarine model featured in several episodes of season 3 and season 5.
It seems that the Kualoa Ranch folks submitted the winning bid at the LOST Auction held back in August 2010.
Ironically, we first see the Galaga in the episode where Locke blows it to smithereens, The Man from Tallahassee. In true LOST fashion, its screen time increases following its demise.
The best view of the Galaga exterior can be found in the episode One of Us in the scenes where Juliet first arrives to The Island.
The Galaga is also present for another important Island arrival -- young Benjamin Linus in the season 3 episode The Man Behind the Curtain. Chronologically this is the sub's first appearance.
In Lafleur, Galaga eavesdrops on the 1974 conversation Sawyer has with Juliet in which he convinces her to stay on The Island for a few extra weeks...
The exiled Charles Widmore leaves The Island aboard Galaga in season 5's Dead is Dead.
Sawyer and Juliet are forced aboard Galaga during the DHARMA Initiatives evacuation of The Island in 1977, as seen in Follow the Leader.
Galaga makes a final appearance in Season 5's finale, The Incident.