Currently watching Monster after just finishing the manga. Also, I'm right in the middle of Gurren Lagann.
Recently watched: Gantz, Trigun, Outlaw Star, Legend of Galactic Heroes
Monster is fantastic(?) but it's kinda hard for me to judge. After reading the manga, I know exactly what's going to happen, so it's lost most of the shock/plot twist factor. Highly recommended, though! It has an ever-growing cast of very well-developed, human characters, and a plot that keeps you guessing till the very end.
Then there's Legend of Galactic Heroes. For anyone thinking that it seems foreshadowing/reminiscent of the Iraq war, you're probably correct. But also correct would be the comparison to conflicts throughout history. Historical war strategies and recognizable command personalities are expertly woven into a narrative highlighting the worst aspects of the vaunted democracy juxtaposed with the best aspects of the corruptible monarchy. Definitely some high-level political philosophy here, but it's entertaining the entire time. And it's set in space. With highly advanced technology, and fleets that send messages on paper (for some reason).
Don't forget the OVA's and 52(!) episodes of side stories, either.