Add to the list if you think I've left any out:
1. The "TMA is too deadly for the street" people. You know them because they say things like "TMA is way better than MMA. The only reason TMA people suffer loss after loss is because they can't use any real techniques in the ring. You know, no iron palm, or eye gauges, or chin na (the small joint kind)
2. The "MMA owns TMA" people. These people say things like "TMA sucks because TMA'ists lose every time in the ring." They usually train in MMA themselves and could probably beat most people on the board.
3. The fortune cookie wisdom masters. These people contribute little, because their answers to everyones questions are in the form of cryptic, psuedo-Chinese master babblings. Someone might ask the question "does anyone have any strategies I can use to improve my sparring?" and the fortune cookie wisdom master might reply "Ah, the dragon who sees his own breath will not be left behind." Noobs may be in awe at the seemingly in depth answer, but from everyone else it will just get a collective "wtf? stfu!"
4. The "my skills are incredible" poster. This person may or may not even practice a martial art in real life. However, on the forum, they are the grand ultimate master who easily defeats opponents all the time. They might (claim to) have an iron palm that can break 10 bricks with no spacers, be able to shoot chi-blasts, used to live in China and trained with a master so secret they can't even mention his name, etc. This person is usually a TMA who has stories of defeating practicioners of all other TMAs, as well as MMAs. They say that weight lifting is no match for traditional kung fu strength building exercises.
5. The "empty cup" poster. This person is awesome and regardless of his or her level of experience, always has an open mind about everything they hear.
6. The lurker. Unknown levels of experience. Unknown styles. May be a 10 time nhb champion or someone who is just becoming interested in MA. But since they don't post, they're lurkers, and we don't know who they are.
7. Trolls. They make the board fun sometimes. Usually they're *******es, but every once in a while you get a good one. They're still *******es, tho. They like to start sh.it, and then let people argue for a while, and then come in in the middle and say the opposite of what they declared before. They either plan it that way, or they're the most illogical, short-term memory-deprived people on the internet.
8. The leg humpers. You can tell a leg humper because as soon as a female announces her presence, all the leg humpers reply in 0.00000001 seconds. Little do they know the "female" is probably not a female. Notice how threads by someone whose username includes "chick," "girl," "grrl," or something of the sort will quickly be filled up by replies from the leg humpers.