Rick Riordan: I loved Percy Jackson, Heroes of Olympus, the Kane Chronicles
Cassandra Clare: Man, I loved the Shadowhunter series. Plus all the drawings on tumblr! But now it's the only series on this list that I wouldn't reread (still like the art though)
Philip Reeve: Predator Cities and Here Lies Arthur still make me nostalgic
I remember Pat Walsh too
Darren Shan: Cirque du freak, demons, vampires, vampaneze, werewolves, magicians, mages, Windows, spiders, pickles, lakes, Desmond Tiny, Kah-Gash... I loved this.
Artemis Fowl, Skulduggery Pleasant, Dresden Files and Alex Verus
I used to read some manga back then too: the big shōnen ones mostly but also stuff like Tegami Bachi, Nodame Cantabile, etc