OVA Series/TM! GXP
Ryoko is definitely a wild one, her name literally means "demon summoner" and can call upon spirits to do her bidding (as long she has a gem on her right hand). She posses other powers like teleportation, energy sword and projectiles, splitting herself, and even fly. If she was to have all three gems, she would be as powerful as Tenchi can. Ryoko is over 5000 years-old (this is in earth years; she did say 2000, but that was with a different calendar) and never knew until recently that she was created by yours truly. She decided to give-up her life as a space pirate to be with Tenchi, and tries everything to grab his attention. For fun, she likes to annoy Ayeka and drink Sake.
TV Series/Tenchi in Tokyo
Sort of an outcast throughout her life, she has turned to a life of crime. An infamous space pirate, she is one of the most wanted by the Galaxy Police and chased by countless bounty hunters. Nowadays she hangs around Earth with the Masaki family, always has her eye on Tenchi (and everything else for that matter).
Note: Ryoko self-named herself Masaki, she is not at all related to the Masaki family.
Pretty Sammy OVA Series
One of my favorite (and lagging) students, she has the tendency to pick fights and show-off to Tenchi. Matter of fact, she has the tendency to kidnap Tenchi too.