The Full Metal Alchemist manga just came out, it's rather good. I'm generally more into the shoujo stuff, so I read things like Rurouni Kenshin and Naruto.

Vision of Escaflowne is absolute crap as manga form, I wouldn't wish that on anybody, lover of mecha or not.

If you like the shoujo Fruits Basket might be good, it's one of the few shoujo I will actually read.

I hear Trigun is good, as are Chrono Crusade and Hellsing.

I can probably think of a few more to post up later. I'll let Starlight give a few of her own suggestions as well, as I'm sure she'll see this thread eventually.