I have played in quite a few Star Trek games and the most common thing that makes me quit are my fellow players. Call me a snob if you will, but I am very picky when it comes to whom I play with. If a player is unwilling to show some creativity in creating his character, I do not want to game with them. If they are playing a ridiculous character, I do not want to play with them. If they have difficulty writing coherent posts, I do not want to play with them. If they ignore me or other players, well, you get the idea.
Here are some examples of ridiculous character archetypes I have seen abused over the years:
The guy from the 20th century. I swear, Starfleet is littered with these guys, men and women who somehow survived hundreds of years in suspended animation or are time travelers. And more than that, these temporal outcasts seemed to be able to handle four years of Starfleet, getting the hang of technology centuries ahead of what they were used to. Before you know it these rock 'n roll listening hipsters are showing up fellow officers with their plucky 20th century values and kick-ass attitude.
I guess I am not the only fan of the old Buck Rogers television series.
The Immortal. Be it an El-Aurian, mutant or the product of some other plot device, they are hundreds of years old with tons of experience under their belt. They have seen it all, can do it all, they are experts at everything. Trills fall into this category as well; every single Trill PC I have seen played had lifetimes of experience in every useful occupation you can think of, from pilot to general to spy. It is sad that these players never actually looked at Dax on DS9 and saw how the character's past lives ran the gamut of different lives, from the exciting (Kerzon) to the utterly banal.
The Super Soldier. They are the best at what they do. They are death on two legs and have no fear, no weakness, no dimension beyond two. They may be pure warrior Klingons or Angosian super soldiers, and their only mission is to turn every first contact into a bloodbath. Often these players gravitate towards games with ships possessing a marine contingent (never mind that in Star Trek Marines were only mentioned once and that was in a scene originally cut from Star Trek VI, and ships like the Enterprise D had no marines whatsoever, and it would be unlikely 21st century USMC insignia would be employed by Starfleet to designate rank, GMs have been using marines on Star Trek ships for years in situations where standard security officer would do just fine) and only care about combat, or looking for every chance to interact with other players in order to show what brooding loners they are. Drama queens.
The half breed. One race is not enough for these people, they have to be half of one thing, half of another. Sometimes they make sense (i.e. half human, half Vulcan, or half Vulcan, half Romulan), but often times it can get pretty ridiculous with utterly bizarre combos that defy biology and common sense both. Klingon/Bajorans, Romulan/Andorians, any chance to make the character unique just for the sake of being unique is just sad.
The rescued Borg. I could go on a multi-page rant about how much I hated Seven of Nine on Voyager (actually, I hated just about everything on Voyager, but 38 of D was near the top of the list), and seeing one player after another running rescued Borg just for the sake of being able to employ those magical Borg
nano-probes was irksome, to say the least.
Players are not the only ones who can make annoying characters; GMs can be just as guilty in creating ridiculous captains for their ships, from the examples listed above to captains who are not even thirty years old. The latest Star Trek movie cannot be blamed for this as I have seen it for years. I believe it comes down to a lack of imagination; GMs who run such young characters are they themselves young and cannot role play "old" people.
When you run a game (and this not only applies to Star Trek, but any), think about what prospective players may see when they check out the character roster. A PC can say a lot about a player's character, and a GM who is not discriminating runs the risk of alienating good players by catering to a host of bad.