Bob

Bob, p.n. 1. short for Robert.
2. (n.) a low level NPC henchman who is seemingly indestructable because the GM rolls really well for it.
3. Any friendly NPC introduced by the GM with the clear intent of killing him off sometime later in the adventure. See also Red Shirt, Spunkmeyer.
4. a person of inderterminate but probably middle age, who does not work (noticeably), instead gaming as much or more than humanly possible.
5. (acronym) Born on Board.
6. J. R. "Bob" Dobbs, patron saint/deity/something-or-other of the Church of the Subgenius. [RR2]
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Addenda: We just keep getting more definitions for "Bob."
Addendum for Definition 2: This goes back to my frosh year at college when a ranger in an AD&D game had two NPC henchmen. They were both 3rd level fighters to our 6 - 8 level party. Bob and Joe had just hooked up with us when we came upon this huge, I forget what it was, but it was nasty. Joe was killed outright, but the thing kept missing Bob. By the end of the fight, the only ones left standing were Bob, the paladin's war horse, and my iddy biddy cleric who hid behind Bob. Our characters became convinced that Bob was actually some powerful multi-classed adventurer who would take us under his wing. Bob's luck held for the length of the campaign. [ME] 
Addendum for Definition 3: This evolved from an adventure run by a friend of mine, in which the pilots of a starship were both named Bob and died quite horribly about five minutes into the session. Since then, Bob has become the name of choice for any NPC who's not going to be around long enough to think up a real name for. [DW] 
Addendum for Definition 4: The "Bob" often vaguely resembles a hobbit or dwarf, and intentionally cultivates a esoteric sense of humor which isn't nearly as impressive if you aren't a sixteen year old weefle-gamer. The Bob is almost always a paleogamer, but rarely actually contributes much to any games he is in. I named this archetype the "Bob" because I have met THREE people so named who fit this description exactly. Brr. [LS] 
Yet Another Addendum: Bungie Games, now more famous for Halo and Halo 2 for the XBox, had a trilogy of games under the Marathon title for the Macintosh. Marathon was one of the few first-person shooters for the Macintosh. The title Marathon came from a generation ship carrying colonists in suspended animation to a distant planet. In the game the crew, who were there to get killed by evil aliens, were called "BOBs," which stood for "Born On Board." A favorite weapon built with the game editor was a BOB Gun, which shot screaming BOBs that expoded once they reached their target. [PG]