Kanon.
Watching now. Pretty nice.

GUNDAM SEED <3<3<3<3<3

Melancholy of Haruhi Suzumiya =D

You should really check Suzuka out, highschool / romance / lilbit comedy and some sports involved. I really love that one and the music is awesome aswell!

you already watched a lot that I would have suggested (TWGOK, MGX, etc.)

high school comedies

Azumanga Daioh

Cromartie High School

high school rom coms

Full Metal Panic (with Fumoffu which covers the side stories probably best fitting since the main plot is mecha action)

School Rumble

Oreimo

college age ish rom coms

Princess Jellyfish

Genshiken (gets more rom com-y as it goes along, particularly the sequel manga)

Moyashimon (...well kind of a stretch but to some degree)

shoujo/jousei stuff:

Ouran High School Host Club

Fruits Basket

Kimi ni Todoke

Kids on the Slope (not a comedy)

Revolutionary Girl Utena (gets mind screwy as hell)

also should probably mention Spice and wolf at some point even though it's not high school or comedy

Durarara!

Lazy Town on Japaneese.

18 + ? Night Shift Nurses

Boku no Pico

SAO is my favourite now:
http://www.instantz.net/watch-sword-art-online-online

OR:
http://www.instantz.net/watch-accel-world-online

http://www.instantz.net/watch-kamisama-hajimemashita-online

http://www.instantz.net/watch-tonari-no-kaibutsukun-online

http://www.instantz.net/watch-code%3abreaker-online

http://www.instantz.net/watch-magi-online

http://www.instantz.net/watch-ixion-saga-dt-online

http://www.instantz.net/watch-k-online

http://www.instantz.net/watch-tasogare-otome-x-amnesia-online

OR THE CLASSICS:
http://www.instantz.net/watch-one-piece1-online

http://www.instantz.net/watch-naruto-shippuuden-online

http://www.instantz.net/watch-gintama-online

http://www.instantz.net/watch-fairy-tail1-online

http://www.instantz.net/watch-hunter-x-hunter-%282011%29-online

http://www.instantz.net/watch-toriko-online

Im sure one of those will get u :D
¡¡¡ Have fun !!!

After thinking for a while I could also suggest Ef-tale of memories also its sequel; if you're looking for something with more fantasy elements Toki wo Kakeru Shoujo - a girl who leapt through time and xxxHolic (these two could fit best to your liking). Also, one named 5 Centimeters per Second belongs to my favourites.

And my previous suggestions stands too. ;)

dragonball z

beserk

i dont give a fuck about your shitty high school garbage, man up

How come no one mentioned Tengen Toppa Gurren Lagann?
I know it's no highschool related at all, but this is one of the best thing out there.

Aoi Sekai no Chūshin de an anime based in Nintendo and Sega characters

Tengen Toppa Gurren Lagann ;D

Chobits

Kore wa Zombie Desu ka

Toradora

<--- That one (WHO CARES IF IT'S NOT HIGH SCHOOL IT'S EPIC)

Or Bleach (got some high school scenes)

Or Pokemon (Watch it if you wanna be the very best)

My Little Monster! High school, Comedey and Romance in one! PLEASE WATCH :D

Nichijou and Danshi Koukousei no Nichijou, two of the most hilarious anime you will ever find... Well imo.

http://anidb.net/perl-bin/animedb.pl?type.web=1&type.unknown=1&type.tvspecial=1&type.tvseries=1&type.ova=1&type.other=1&type.musicvideo=1&type.movie=1&show=animelist&orderby.rating=0.2&orderby.name=1.1&noalias=1&do.update=update&catid.21=100&catid.198=100&catid.17=100

Filtered by comedy, romance and school and ordered by rating, have fun xD

HighSchool , Romance

Bleh.

Death Note its very popular and everyone says its cool http://www.youtube.com/watch?v=HK3lkfhX_XY