In terms of "best" strategy, I would have to say Brian and Rich.
However, the Survivors that entertained me most with the way they played the game were Greg (S1) and Lex (S3.) They had that "Is he a psycho or does he just play one on TV?" quality that I enjoy. I like the contestants that make me laugh.
Worst, in my opinion would be BB (S1) way too crabby and bossy from the start.