I Thought they all were tough and worthy rivals for Satoshi/Ash and they helped him get stronger and even learn more about his Pokemon and himself and even them and even by the end they gained respect for each other (even though Shooty-kun/er Trip is still the way he is the BW series is far from over.) each were tough each provided a challenge and obstacle for Satoshi but if I had to choose it would be Shinji-kun/Paul.

well...gary was more of friendly rival...but it was still fun to watch...trip...dnt know yet :/...barry...was more annoying than anything...but paul gave ash the most trouble...nd disrespect...but paul forced ash to take his stragety nd the belief he had in his pokemon to new levels in order to beat him...therefore i choose paul as ashs toughest rival to date

good choices!

Garys the origanal

To be honest.