It's basic, necessary, irreplaceable, versatile, and comes in all shapes and sizes. It's likely one of the first items you thought about when getting "ready" for summer and should be one of the first items that goes into your bag for travel and any overnight foray.
My go-to tee for the last four or five years has been the J.Crew perfect fit v-neck tee...but alas I am expanding since they have not seen fit to cut me in on the profits from my evangelizing!
A new favorite (I only own one) is the Isabel Marant linen tee - it's a hefty spend but it feels and looks perfect!!