Try: Aspirin Id - ongoing Witch Hunter Killt - not scnlated though inu yasha - its long but its completely scanlated so u can finish in a week or two. Angel Densetsu- this is quite old, i bet u've read it...its hillarious. Star Ocean: Till the End of Time - is good but its sci-fi with outer space stuff dunno if u'd like it or not
well i suggest to read ID and witch hunter and angel densetsu (if u have'nt tried it) first.
Dude, Slayers is where it's at . That series is old school, but it's got everything you've asked for. It's not necessarily shounen or shoujo, though. Definitely some of the most cracktastic and memorable humor, ever.
On the flip side, I'd recommend the anime over the manga.