Sherman Douglas.
Now understand I was young, I grew up in LA and a lot of laker fans I knew were certain he was signing with the lakers and were really excited about it.
More recently I would second those who said Posey. As pumped as I was about Ray and KG it was the Posey signing that I felt was that final piece (solid role player):that was necessary for a championship team. It was then that the potential to win a championship got real for me.