I like the negative way Wakka reacted to the party going up against characters like Seymour and Yunalesca. With most all the characters determined to stop influential leaders without question, it seems so out of place that it was a good comic relief. I liked his accent as well.
And I agree, I think his opposition to them doing that made him more realistic; I mean, a lot of people IRL would not just suddenly go against a leader without hesitation after being used to that leader being an integral part of the status quo for so long, they'd at least question it a bit first. Plus, he was extremely useful in battles; I almost always had him as one of my team of three due to his attack power and speed.