Abridged Arena Array: It's not uncommon to find some servers that overwhelmingly prefer to play maps such as "TTT_Minecraft_B5" or "CS_Office". Some have gone as far as dedicating themselves to only one of these two maps.
Since everyone in Terrorist Town is, well, a terrorist, wouldn't that make the traitor of the group a good guy? Their main objective is to kill off the other terrorists after all, even if it results in their death. So would that mean that the "innocent" are actually the bad guys?
Some fans subscribe to the alternative theory that the game is really Evil Versus Evil, with the traitors being from another organisation.
The fandom gets contentious over "point shops", since some of their additions are seen as stupid or impractical; those that aren't stupid or impractical can interfere with the game, such as a mod that allows you to be a packet of Doritos and thus really hard to shoot in the head. Others, however, do not mind so much.
The Suicide Attack bomb is named the "jihad bomb" on most servers, but a few have renamed it to something else for fear of potentially offending anyone. This tends to create debate on any server's forums.
The idea of "traitor testers" is also quite divisive amongst the fandom. While some like it for possibly simplifying the game and allowing some to prove their innocence without a Cowboy Cop detective trying to kill them, others feel that it makes the game harder for the traitors since the machine can instantly give them away (or do so by proxy after most are tested). Servers typically implement rules that prohibit you from killing someone for refusing to go in and/or destroying a tester, which itself causes further arguments:
Why should an innocent refuse to go in a tester or sabotage their own team's efforts only to be granted immunity? Why would an innocent even think this is a good idea? Should maps with testers be used? Typically, the only way this gets resolved is for the admins to declare "our house, our rules" and ban any naysayers if the debate gets too heated.
Some of the more popular maps such as "cs_office" or "TTT_Minecraft_B5" have come to split the base. Are they classic maps that manage to stay in rotation because they are good and not too complicated, or are they overplayed in favour of some lesser-known maps that might be more fun?
Is the Karma Meter actually useful for preventing RDM, or does it just punish the victims more for taking out a rule-breaker that was trying to kill them for no reason?
On that note, preemptively killing players that repeatedly RDM typically splits fans quite quickly. Those against the practice (typically moderators) point out that this is supposedly not much better than what the offenders are doing (which typically ends in harsher punishments for the "vigilantes" than it does any genuine rule-breaker), whereas those in favour (a large number of players) point out that admins are not necessarily on to deal with cases of RDM all the time and that they would not be doing this unless the offenders had been repeatedly ruining games.
Crosses the Line Twice: There's a certain humor to be found in reading the phrase "Lovable, innocent terrorist", ignoring the weapons such as the jihad bomb.
Evil Is Cool: Most people will readily admit that while being an innocent or a detective is fun, they really enjoy the traitor rounds.
Overlapping with Difficult, but Awesome, C4 is notoriously powerful, and even capable of killing players through walls and iron doors as long as they can hear the beeping, to the point that some servers have nerfed it.
Traitor testers have become a subject of debate amongst many players of the game; whereas they can be sabotaged and most servers won't ban you or kill you for sabotaging/destroying them, they do make it remarkably easy to work out who is innocent and then kill anyone left once some basic mathematics has been done.
Massive Multiplayer Crossover: As TTT is part of Garry's Mod, players and server admins can download a myriad of characters and items from all sorts of different things, ranging from franchises to internet memes to real life objects for players to use in-game, although this can become unfair to play against (See: Broken Base entry on this page).
The entire game if you're an innocent. More than a few accidental teamkills will result from this. This also applies if you can't hear anyone else and think you're the last one left.
The other "classes" have this same issue. If you are a Traitor, most of your time will be spent trying to commit your crimes wondering "are they going to figure it out?" and looking over your shoulder for witnesses. The Detective meanwhile has to find the Traitors as fast as they can, all the while having a massive target on their back since the Innocents will be crippled without them.
Jihad bombs, if your server has them installed and many people run close together.
The sound of beeping means that there's C4 somewhere, but unless you're a traitor or have a defuser kit, you have no idea where it is. Similarly, attempting to run and hide may be futile, since the explosion can travel through walls and iron doors. The only real way to not be killed is to make sure that you can't hear it and then run even further, since anyone within earshot (and just out on occasion) will die.
"Stop Having Fun" Guys: Some parts of the fandom are very vocal about certain Let's Play videos, in part because of RDM note "random death match", done when someone is killed without legitimate reason, ghosting and the use of communication programmes other than in-game voice chat or typing. See below:
SeaNanners is probably one of the more notable examples, since he caused the game to rise in popularity, causing his impressionable fanbase to copy him in committing RDM, not playing as the game is meant to (such as getting people killed for prop racing) and so on. For further context, Nanners plays on a private server with close friends, whereas his more irrational fans join random games with strangers and are seen to unbalance the game with behaviour that will result in a pretty instant ban.
The Yogscast have come under fire for this as well, due to a similar Colbert Bump, though their behaviour has improved since. Weirdly enough, this doesn't apply to Achievement Hunter's playthrough, where the most complaints about their behaviour seemed to come from players in their game.
The irritation about bad behaviour doesn't just extend to fandom reaction. Some more extreme fans want the gamers in question to stop doing it on their own, private servers, when everyone is okay with it.
What Do You Mean, It's Not for Kids?: Despite the game being fairly graphic, with some fairly gory stuff (reaching Gorn levels depending on the server), there are a notable number of servers that try to be as child-friendly as possible by enforcing a no-swearing rule, even though a terrorist may literally shout "SHIT" upon dying. Typically these servers are ridiculed, and one of the very few things that the TTT fanbase can agree on is that these servers are Dramatically Missing the Point.