I'll start off with two:
What If #1:
Let's say in 2009 the Thunder win the NBA Lottery. So instead of picking Harden they chose Blake Griffin.
This would have left them with 3 legitimate NBA stars who are all extrememly young.
There starting 5 would've been something like:
Westbrook
Seflosha
Durant
Griffin
Ibaka
I think had this happen the Thunder would have won at least three titles in the next ten years.
What If #2
This year the Clippers traded there first pick and B. Diddy for Mo Williams. Well, that pick ended up being #1 in the NBA Draft. If that trade never happened, the Clippers would have likely chosen Kyrie Irving.
Had they chose Irving they would have had a lineup like this:
Irving
Gordon
Aminu
Griffin
Kaman
Bench: Davis, Bledsoe, Foye, Jordan
If they would then be able to trick someone like the Hawks into doing something like Kaman, Jordan and 2 first rounders for Horford...Oh boy.
And a third possibility for a 'What If':
What if the Grizzlies don't trade Kevin Love for OJ Mayo. Then next year they pick someone like Tyreke Evans instead of Hasheem Thabeet...
