(Bah, I posted here before. Didn't realize. Oh well.)
Only five?
I have, like, ten that's all tied for first. xD
Watanabe Yoshitomo -- Cuteness at its best! Though some of the plots seem overused at first glance, it always somehow manages to turn into something completely unique and interesting. It's like my mind is being read and everything I like about the shoujo genre is incorporated into such amazing manga. My favorite is Beyond the Beyond, but I also have a liking for Fun Fun Factory.
Mizu Sahara/Yumeka Sumomo -- Such endearing stories, and beautiful artwork. I love how she writes, and I always seem to gain something with each rereading of her works. Her shounen-ai stories are always oozing with cuteness as well. <3 Favorite must be her one-shot "Robot" from the volume collection "Natsukashi no Rozione".
Takahashi Tsutomu -- There's no words to describe how much I love his works. They're always so amazing. Favorites are Skyhigh, Blue Heaven, and Jiraishin. (Yes, a tie between three. x3)
Toume Kei -- I really, really like her art style. I think it would be really suitable for a dark, morbid, horror story. But, she doesn't write those. Her works are a bit dark, sure, but there's always a certain amount of brightness in them, a happy ending, so to speak. It kinda caught me off-guard at first (I didn't really think the art style matched), but after a while, I realized that it was absolutely perfect. Favorite of hers is Hour of the Mice and Acony. I really liked Luno too.
Kunieda Saika -- I just simply love her stories. Though I do get a bit disappointed with her comedies, her dark stories are what I live for and feed off of and worship. They're so wonderfully dark and morbid that I'm in ecstasy whenever I read them. I really loved Mirai no Kioku and Kaze no Yukue, nevertheless, though the one-shot collection "As the Time Will Come the Rain Will Fall" captured my heart and soul.
...There, five. Kinda wanna name Kaori Yuki, though, but I've been a bit disillusioned with her works as of late... Hm...