Sword Art Online (Anime and Light Novel) I'm a huge fan of SAO, for that fact that Kirito always beats his challenges by thinking outside the box, and occasionally with brute force. I recommend the series for anyone that is looking for a light mix of action and romance. The novels are where things start getting really interesting, exploring the social and technical issues and applications of full-dive VR technology and Artificial Intelligence.
+1 to Black Lagoon. I liked it for the variety of strong characters, and especially for Rock's character development. He went from being a totally average dude, to being a totally average dude that learned how to use his totally average skills to be a powerful and indispensable asset to the mercenary group.