Enyalus
MALE DOMINANCE!!!
Yoda vs Sion (location Malachor V) - Based on the persuasive argument of others that Sion wouldn't be able to pull himself back together and continue fighting, Yoda wins.
Yoda vs Kreia (location Malachor V) - I think Kreia will win. She can Force Sever practically instantly. We don't know if Yoda would be able to resist it or not...
Yoda vs Star Forge empowered Malak (takes place on the Star Forge where Malak fought Revan) - Yoda wins. His saber skills are still above Malak, and if Yoda was able to stalemate Sidious in the Force, a StarForge enhanced Malak won't fare any better.
Yoda vs Exar Kun (takes place on Onderon) - If Kun uses his amulet, I think Kun wins. If not, Yoda does. My reason being is because his amulet strikes a rather large area, and although Yoda is blindingly quick, I don't know if he's fast enough (whatwith small legs and all) to avoid being struck by it. That would at least daze him, and Kun would finish him off. Otherwise, like I said, Yoda wins.
Yoda vs Bane (takes place on Korriban) - Bane wins. Maybe easily. Bane is 6'7''. Would Yoda even be able to jump high enough to decapitate him? Without completely telegraphing his attack?
If the answer is yes, then Bane only wins a very close match. A battle meditation amped Raskta was being pushed back under Bane's onslaught. Given the fact that she was the best duelist in the Order at the time, the fact she was BM amped, and the fact that she wields two blades instead of one, to me means that she would be about Yoda's equal in saber skills at that point. Plus, Yoda is old and can only fight at a high level by tapping into the Foce for a short amount of time. Bane's orbalisks, meanwhile, just make him stronger and fuel his dark side powers.
Not to mention that if Bane got really pissed, his Force Scream is stupid powerful.
That's my two cents.