The straight A-2-3-4-5.
It is the weakest straight for the high hand, with the ace played as 1, and in Hi-Lo it is the best low. Example. In Omaha Hi-Lo on a board of A-2-3-4-5, any 2 cards from A to 5 in your hand make a wheel low. It is also the best hand in Razz and A-5 Triple Draw.