The Actor: This player cares less about the rules or character optimization and prefers to make character they are interested in playing, which they do with gusto and vigor often launching into long descriptions of what his character is doing.
GM Notes: The Actor can help bring a feeling of realism to the game but it's important to balance allowing them to have their time in the spotlight without allowing the game to become the character's autobiography.
The Lurker: As describes in the question, the lurker is generally a player who attends a session, participates in a minimal fashion and is usually gaining enjoyment simply by hanging out with other people to see how the game goes.
GM Notes: The Lurker can be hard to read at times, just because they haven't stepped out to involve themselves in the game so much should never mean they don't get the opportunity to do so, while on the other hand some lurkers are content to just lurk and shouldn't be forced into the spotlight.
Rules-Lawyer: A rules-lawyer is the type of player who believes all rules must be obeyed as all times and seems to know every rule by heart.
GM Notes: The rules-lawyer can help provide structure to your game, though can tie the group down into mostly meaningless arguments. This is better dealt with in private if you feel excessive rules-mongering is hurting the campaign.
The Munchkin or Power-Gamer: This player has spent hours going over source material and rules and typically builds characters that are highly specialized. They might not be useful for most other things, but will decimate a particular type of challenge. They are typically very knowledgeable of the rules which may cause you to think they are a rules lawyers, but they only point out the rules that are to their own benefit.
GM Notes: It's virtually impossible to take on a munchie in their field of expertise without being detrimental to the rest of the party... and they can tend to make other players feel useless. Make sure to design a well rounded game where the munchie isn't in the spotlight at all times. They are typically one-trick ponies, but will hop on that pony for a ride every chance they get. Don't allow them to overshadow the other players that want to participate by building challenges unsuited for the munchie's character, but don't cut the munchie off completely else he'll feel as useless as his cohorts did when he was always center-stage.