Iwata is the best character (besides the major ones) in the series.
Excel Saga spoilers ahead:
Spoiler:
Kinnda off-topic but was any one really surprised when Iwata died in the manga? I know I was. Man, that death came out of nowhere.
Spoiler:
Yeah, the manga never ceases to amaze me. I didn't think you could do that to important characters in comedy mangas, kinda ruins the mood. However, when he came back in Ropponmatsus body I was laughing harder than ever before. Most awesome thing thought is when Watanabe turns into a sadist.