The Kingslayer + Drogo vs The Mountain + The Viper

Team 1 wins Jamie beats the Mountain and Drogo beats the Viper. I think Drogo is the type of fighter that would actually give Oberyn a challange here and his strength speed and ferocity would overwhelm the Viper. For people calling Khal Drogo the weak link, this is a man who has never lost a fight since birth and seems pretty eager to fight. He died due to infection and blood magic not another warrior.

Team 1 dies a few days later considering the Viper would be sure to at least knick both of them with a poisoned blade.

Everyone Dies.

I'd go with Team 1 in this.

depends on the book or show variants. Book variants team 1 win, Jamie can win over mountain or the viper while Drogo can keep the other one occupied. If we go by show feats though team 2 stomps simply because Team 1 have about 0.5 good feats where the mountain can murder them both based on feats.

I'd have to say Team 2 for both tv and book versions. Jamie and Drogo are both extremely skilled in their combative arts, that being said, Jamie has listed The Mountain among the small list of people who he thought could best him. If Drogo was used to fighting in armor and against armored opponents, I think I would give team 1 the advantage, but since it's foreign to him, I don't think he would last. I believe he could hold his own, but without armor of his own he would probably be cut down. Not to mention, the weapon choices. 6 foot greatsword and 8 foot spear vs a 4 foot longsword and a probably around 3 foot arakh. The reach advantage is outstanding. I think Drogo would have a better chance at closing distance than Jaime, as he likes to get up close, but since Oberyn is probably faster with a poisoned weapon and Gregor is armored, it wouldn't matter much. Jaime would have difficulty closing distance with Oberyn without being cut by his poisoned spear, due to his speed. And if he did close distance with Gregor, the extreme strength difference would overwhelm him.

Honestly, I'm surprised Eddard isn't considered to be in at least a top ten. I know he was never remarked to be an exceptional swordsman, but in the show, he was able to stand on even terms with Jamie, even getting inside his guard close enough to push him away. Replace that push with a dagger and it would have been Ned riding away from that battle. And although the details on the tower of Joy are vague, Eddard possibly defeated Arthur Dayne, thee most renowned swordsman in Westeros, in almost single combat. I'm sure Howland Reed assisted him in some way, though the Reeds are known for not fighting directly. Maybe he poisoned Dayne during the fight somehow or was able to stab him in the back while Ned kept him occupied. Either way, holding your own and defeating Arthur Dayne should warrant some recognition as an excellent fencer. Granted, you could bring up the fact that Ned and Rodrik lost a sparring match with Bronze Yohn, though that took place 13 years after the tower of Joy. Ned may have fallen out of practice as he got older and he never seemed to be a man who preferred violence or had his fill of it in the rebellion, so I doubt he had much of a desire to practice his swordsmanship when there was no need of it.