No manga collection can be complete without...

...having Yumiko Takahashi's Lum Urusei Yatsura sitting on its shelf.

This series is both sexy and funny and has everything a manga fan would expect out of a great storyline.

Unfortunately this series is getting harder and harder to find as it's currently out of print.

It's like Sailor Moon only for adults, and I mean ADULTS!
This manga is borderline XXX rated in some issues and can be pretty smutty with both the visuals and the language, but it never crosses the line.

Currently Amazon has a few used copies available.
Ebay or your local manga shop might be a better source to find this fine manga series.