I just recently finished the game and - For some strange reason - At the part where Booker rescues Elizabeth:
Booker: "You can't kill Comstock, it's too dangerous."
Elizabeth: "Oh yeah? And what are you gonna do to stop me?"
Booker: "Not a damn thing, because I'm going to do it for you."
Granted, that probably isn't the exact dialogue, but THAT'S when my shipping feels kicked in and I just hardcore shipped them throughout the rest of the game.
So.
I looked up Booker and Elizabeth on here - Bioshock, in general - And I was really disappointed to not find anything. However, if you're like me, and looking for some REALLY AMAZING BookerxElizabeth smut, *whispers* go to Fanfiction.net *clears throat* Then you're out of luck.
Wink, wink.
Nudge, nudge.
So, if I can get a decent amount of messages or comments on my profile - WHATEVER - from some fellow Bioshock Infinite fans / fellow shippers of Booker DeWitt and Elizabeth, then, well...
I'll be sure to give them a story worth their time.