Without knowing their tastes or where they are from I always say Cowboy Bebop is the safe bet. It doesn't feel as foreign and has a very western vibe that won't be as big of a culture shock as other anime. Odds are it has something you like whether. It's got action, touching moments, comedy, a great story with underlying themes and messages, an array of unique characters, and doesn't take itself too seriously. It's my favorite anime but that's not the main reason why I recommend it. I recommend it because it feels very western and seems more like dipping your toes rather than diving in head first into anime.

The first time I saw anime it was a random Inuyasha episode on adult swim as a kid and my thoughts were what the fuck is going on? Even though it was a dub I was incredibly confused by all of these made up terms and story aspects. With Cowboy Bebop you can start at pretty much any episode and pretty much grasp what's going on.

TLDR: Can't go wrong with Cowboy Bebop. It's amazing and it's easier to digest if you are knew to anime.