Kurau Phantom Memory - just rewatched this again last week...
Hellsing and
Hellsing (2006) - I would watch both (TV before OVA) but if you're not much interested, just watch the OVA (more manga-accurate retelling of the story)
Juuni Kokki - like the best anime ever aired
Trigun - like the second best anime ever aired
Mushishi - Mushishi
Kino no Tabi - Kino no Tabi
...like Pellissier said, a few to start. I must say you have have plenty to watch without resorting to "lesser known titles" for quite some time.