There's no point in just rattling off good series; it really depends on what you like. It also depends on what you're willing to spend.
Having said that...
If you stocking up for a marathon session, I'd suggest any of the following.
Cowboy Bebop. It's available individually or in a six-disc set (no idea about video), with a free audio cd. It's a detective series set in the future, where mankind has colonised most of the solar system. Great characters, great story, excellent soundtrack.
Urusei Yatsura - Rather silly; but my favourite series. Lum is an alien who challenges a random earthling to a game of tag to decide the fate of the Earth; she then falls in love with him. Wackiness ensues. Millions of episodes, a lot of them available on DVD/video.
Tenchi Muyo - You should've heard of this. You should've seen it. It's great.
Gunbusters - Available on three tapes/one disk; it's a truly excellent space opera. It's from Gainax, so you know it's good.
Films; too many to count, Ghost in the Shell, Akira, Patlabor 1&2, Wings of Honneamise, Princess Mononoke, My Neighbour Totoro... the list goes ever on.
