I haven't seen a character yet who put 8 in CON using point buy. I have seen every other stat get an 8 from at least somebody.
(Not an exhaustive list)
8 STR: Wizards, Warlocks, Archer Rangers
8 DEX: Wizards, Warlocks
8 INT: Everybody except Wizards, Warlocks, and Taclords
8 WIS: Artful Rogue, Feylocks
8 CHA: Rangers
But everybody could use a little CON. Most characters will take at least 12, and I've seen a lot of 14s for that extra surge. Any axe-wielding character who also has high STR will want 17 by epic. Starting at 14 also means deadly axe is available at 11th.