Ouran High School Host Club could be the funniest anime I've ever seen, although One Piece tops it at moments. It's just that OHSHC, or the anime anyway, was funny the whole through. Didn't really take itself seriously. Not until a point in the manga where the anime had long stopped.
Boring is hard for me to define. I just tend to drift away from series and get back into them a little bit. One anime that is supposed to be hilarious but is notorious for just being unfunny to me is Gintama. but it has its moments. Believe it or not I much prefer it when it takes itself seriously as opposed to when it's trying to be funny. Some of the jokes are funny, but just not enough to carry me through entire episodes.
I'd have to say either Bleach or DBZ. Bleach has a slightly more complex story, but really it seems very reminiscent to DBZ in the way the events play out - I often joke how it's like DBZ with samurai swords.
*please don't shoot me, if you're a fan- I watched both series for a while, myself, else I'd not be able to judge them much*
Most of the boring series I started watching I dropped. Kobato. being the most recent series that I found that dull. Although Bluer than Indigo was extremely dull and I watched that series and its sequel...