Of all time for me it is Ken Griffey Jr during his mariner days mainly. That guy fascinated me so much at a young age. He was so exciting and I think he is one of the all time greats. If he had cheated like a lot of his counterparts in that day he would have shattered the home run record in my book. I also liked Mariano Rivera and Derek Jeter.
As far as current players? I honestly don't know. I'll have to think and post a comment on that one later.