Which of Ash's Pokemon should evolve or stay unevolved?

[TPrower]

As we currently know, Ash has Pikachu, Snivy, Tepig, Oshawott, Scraggy, and interchanges between Tranquill and Swadloon. Which do you all think should stay the way they are or evolve? Personally, I think it'd be fitting for Ash to have an Unfeazant and Leavanny, but I feel Oshawott shouldn't go farther than Dewott, and Snivy and Scraggy should stay how they are, since I feel they're better that way. As for Tepig, if we remember Ash's other Fire starters, it's not a stretch to think he may end up with an Emboar in the end.

 

[Musashi]

http://bmgf.bulbagarden.net/showthread.php?t=30262

We already have a thread for this.