It is a shame they only got to play late in Allen and Garnett's career, but Pierce, Allen, and KG should be mentioned. Can only speak of what I have seen (starting early 80's) and my choice would be Magic, Worthy, and Kareem.
Short-lived, but I'd have to pick West, Chamberlain and Baylor. You have three players who are each one of the top-three players ever at their positions.
I think Zbo, his boy Love of the Hoops Family, and AF(AKA Jane Doe) is one of the greatest threesomes in NBA history. Consider the evidence: