Lvl 68 for the majority of sources. Only loot goons and loot midgets can drop lvl 69 weapons.
EDIT: And some "Items of the Day" in weapon vending machines can be lvl 69. At least they were available in the lobby of The Underdome of DLC2 Mad Moxxi's Underdome Riot the last time I visited.
Drmaxman 06:58, May 5, 2012 (UTC)