Suzuka and Pastel are an absolute must.

I might be opening pandora's box by saying this but Suzuka and Pastel are terrible

Well I'm assuming you are hinting towards comedy/romance shounen with possibly a harem on the side
To-LOVE-Ru - Well umm not to heavy on the plot but hell a lot of ppl like it
School Rumble - I hear its good, from the 4 chapter I forced myself to read it seemed similar to the parts of Love Hina I managed to read . . .
Rosario+Vampire - Amazingly another one I have read, good comedy, harem, and enough fan service to almost be annoying
I"s - Romance/Comedy, been a while since I finished it but I remember thinking it was worth while
Ai Kora - Funny as hell, a little romance (not to much if thats all you want), but I couldn't bring myself not to include it in the list
Pretty Face - Funny, not really to much of a harem, and to be honest I can't remember if theres fan service, but hell a guy thats surrounded by god knows how many girls most of the time, I'm sure theres some
Omamori Himari - Well you said no Hentai, and this IS a shounen, but its written by a mangaka who basically has only done hentai up to this point. Its basiclly fan service in a manga, and dont worry, it is kept PG-13 for the most part

Note: Ignore my bitter attitude, these are all infact good and highly recomended manga for you, I'm just a bitter person

I support you, so if you did open Pandora's box, I'm with you

I think B Reaction is like Love Hina. I mean it has comedy, romance, and action. Though its only 2 volumes.

yeap, love hina, suzuka,and pastel are ones of the best manga to start with. plus they have a great story line and ending that make scenes not like other manga like like. well i cant think of a tittle right now but u know what i mean. i think