Mr. Pointy was the stake that was owned and possibly carved by Kendra Young. Kendra claimed it was her lucky stake and said she had killed many vampires with it. It had a notable curved end. Kendra gave it to Buffy Summers to kill Angelus. Buffy intended to stake Angelus with it if Willow Rosenberg could not restore hissoul, but didn't when informed of the trap Angelus had laid.
Buffy kept it for a long time after Kendra's death, having it bronzed in honor of Kendra and, according to herself, keeping it as a safety blanket.
In "Helpless", Buffy claimed to have had the stake bronzed, while in "Choices" and "The Freshman" she mentions to have used the stake against vampires which would not be effective. It is likely she was just colloquially referring to any generic stake she had.