HBO's Game of Thrones - Page 47
I don't think Syrio is on Jaime's radar, but that guy could take on the Kingsguard with pool cue.
Bronn is also off Jaime's radar, but he himself thought he had a chance against the Mountain.
Reaching into the books, there's (deceased) Arthur Dayne. (arguably the greatest of all knights)
When asked who would win in a duel, George R.R. Martin said that if Arthur Dayne and Barristan Selmy fought with any swords it would be a very even fight - but if Dayne was armed with his sword Dawn, he would narrowly have the advantage over Selmy.