Here are just a few examples of the kinds of fallacious dub arguments we've heard and used ourselves when we were dubs.
Heck, the WHOLE DARN RELIGION is nothing but a series of fallacious arguments!
ad hominem - (attack the arguer, not the argument)
"Since apostates have abandoned Jehovah, they are of their father the Devil and nothing they say can be trusted."
appeal to ignorance - (if an assertion has not been disproved, it has to be correct.)
"No one can prove Jehovah doesn't exist. Therefore, he must exist."
argument from omniscience - (the arguer tries to assert it knows everyone's actions or beliefs)
"All apostates are out to destroy Jehovah's earthly organization." (Many apostates don't give a rat about dubs!)
appeal to tradition - (people have believed something for a long time, so therefore it has to be true)
"Because of the rich spiritual heritage of Jehovah's organization, we can be sure our beliefs in these last days are approved by Jehovah himself." (Or as Mark Twain might say, "if millions of people over a hundred years have believed a stupid thing, it is still a stupid thing.")
appeal to authority (citing a dubious "authority" to help confirm the argument)
"A noted scientific journal stated that blah, blah, blah."
(That unnamed "scientific" journal was Popular Mechanics! The WTS is notorious for using this kind of argument and not citing the source. In one example, the WTS cited an "authority" that when tracked down, turned out to be Reader's Digest! In another, it cited a newspaper which stated how much earthquakes have increased in the 20th century. It turns out that the newspaper's source for its information was taken from the Awake! magazine!)
argumentum ad baculum (using fear as the basis of an argument)
"Those who don't come into the safety of the Spiritual Ark will soon be destroyed by Jehovah at Armageddon."
circular reasoning or begging the question (the assertion assumes the conclusion)
"Jehovah has an earthly visible organization and we must follow it, because this organization was appointed by Jehovah himself."
confirmation bias (using only some examples that confirm an argument, but ignoring all others that disprove it)
"Sister Jones wanted to pioneer, but didn't have a car, so she prayed to Jehovah for help. Within 2 weeks she had herself a car. So you see, Jehovah does answer our sincere prayers." (While Pioneer Sister Jones was praying for a car, Pioneer Sister Smith was praying for her life right before she was brutally raped and murdered.)
loaded question (any answer to a question will imply agreement to it)
"Those like you who left the organization hate the organization and Jehovah. And you haven't stopped hating Jehovah either, have you? (A "yes" answer implies the person hated Jehovah in the past. A "no" answer implies the person continues to hate Jehovah)
non sequitur (the conclusion does not necessarily follow from the assertions)
"The Bible states that crime would rise during the last days and so it has. Therefore, we can confidently say crime will continue to rise even further until it is so far out of hand that Jehovah will have to destroy the wicked at Armageddon."
red herring (diverting the argument by changing the subject)
Opponent: "None of your JW predictions have come to pass."
dub: "The Bible says that there would be many ridiculers in the last days, and people like you prove the Bible to be true."
(The argument was about JW predictions, NOT about ridiculers.)
slippery slope (unproven adverse consequence will occur if something happens)
"Those who leave safety of Jehovah's visible organization soon degenerate into debauchery, including adultery, crime and drugs."
special pleading (the one making the assertion wants an exception made [which he cannot reasonably justify] to standards he applies to everyone else)
"Jehovah gave to Bible to all of mankind so they could read it and gain his favor, but only Jehovah's Witnesses are able to understand the true meaning of the Bible."
straw man (misrepresenting the argument and then attacking the new argument)
Opponent: "The policies and doctrines of the WTS are harsh and unreasonable."
dub: "It is hard to be one of Jehovah's Witnesses and many people are unwilling to put in the hard work it takes to be one of us. The Bible says that lazy people will not receive salvation."
(The opponent was talking about harsh and unreasonable doctrines, NOT hard work.)
false dilemma (assuming there are only two possibilites when there could be more)
"You've been studying the Bible with me for over a year now. It's now time for you to decide if you want to become one of Jehovah's Witnesses or receive eternal destruction from Jehovah."
questionable cause (if b happened after a, then a must have caused b)
"Brother Russell said the Gentile Times would end in 1914. World War I started in 1914. Therefore we know the Gentile Times Ended in 1914."
(The fallacy is that the dub thinks WWI was caused by the ending of the Gentile Times, when there are many other possibilities for its cause.)
subjectivist fallacy (a claim that what is true for everyone else is not true for the arguer)
dub: "Lying is wrong and the Bible says liars will not enter the Kingdom of God."
opponent: "But you lie to your enemies."
dub: "Jehovah allows his chosen people to lie to their enemies."
the undistributed middle
"All true Christians preach the Kingdom message."
"All Jehovah's Witnesses preach the Kingdom message."
"Therefore, all Jehovah's Witnesses are true Christians."
In this case "true Christians" has not been defined as to all the things it includes. It may also include the requirement that to be a "true Christian" one must have to show charity towards others, and so forth.
A more obvious example would be:
"All humans have two legs."
"All ostriches have two legs."
"Therefore, all humans are ostriches."
The set called "two legs" may contain more animals than just humans and ostriches. Likewise, the set called "true Christians" may contain more requirements than just preaching the Kingdom message.
Farkel
Farkel,you are among my top 5 favorite JWD posters keep up the good work!
Remember The 8 marks of a mind control cult:
WT$ 'anachronistic alchemy' quantum quackery' and their 'gospel of gobbledygook' i.e.Christ Jesus did NOT return to power in 1914 the central CORE doctrine of the foundation of the "House" of Watchtower.
Quantum quackery: fundamentally flawed fallacies 
The "Quack" test: If it Quacks like a Duck................