In a severely misguided effort to refute the deity of Christ, the New World Translation conveniently renders John 1:1, which typically reads "...and the Word was God", as "and the Word was a god." (Emphasis mine).
It's no accident that this is the only translation that does this. It is a deliberate mistranslation on the part of the Watchtower Society, who of course refuse to release details on who produced the translation, completely avoiding any accountability. Nevertheless, in doing this, they have still shot themselves in the foot.
A question that must be asked is how many gods are there? There are a few ways to answer this question, each depending on how you define God. Needless to say, the Bible is inherently monotheistic. If you call Jesus a God, you are calling Him the God.
But there is a sneaky way in which Jehovah's Witnesses may sneak around this. After all, there are several ways in which the Bible does describe "other" gods, even calling Satan himself the "god of this age". So, is it possible that John was referring to Jesus in another sense of the word "god"?
Evidently, Jesus is not the "god of this age" in the way that Satan is the god of this age. We even see during Jesus' temptation that Satan offers part of his domain if Jesus would only worship him (Luke 4:6-7), so aside from the obvious distinction between Jesus and Satan, even their authority is distinguished between. This, therefore, is out.
Another way the Bible refers to other gods is similar to the way we do. Man made gods are still called "gods", whether they be lifeless idols (e.g. 1 Corinthians 8:4) or living beings that are called gods (e.g. Exodus 12:12, wherein the "gods of Egypt", such as the Pharaohs, are judged). This, again, is an unsuitable application. In Isaiah 42:8, God declares that He will not share His praise or glory with idols, and yet in John 17:5, Jesus asks to not only be glorified with the Father, but actually claims to have been glorified with Him before the world even began.
Which brings us to the third way the Bible uses the term "god" in a non divine sense: A being with special authority. It is interesting to note that this very thing was discussed by Jesus and the Pharisees. Having declared "I and The Father are one" (John 10:30), Jesus angered the Pharisees, who began picking up stones to stone Him. They even explain why: "For a good work we do not stone You, but for blasphemy, and because You, being a Man, Make Yourself God." (v33, emphasis mine). (The New World Translation also corrupts this phrase).
The Pharisees, therefore, recognised Jesus' divine claims. Jesus claimed to be God, the Pharisees recognised He was claiming to be God, so they picked up stones and tried to kill Him. But Jesus defended Himself: "Is it not written in your law, ‘I said, “You are gods” ’? If He called them gods, to whom the word of God came (and the Scripture cannot be broken), do you say of Him whom the Father sanctified and sent into the world, ‘You are blaspheming,’ because I said, ‘I am the Son of God’? If I do not do the works of My Father, do not believe Me; but if I do, though you do not believe Me, believe the works, that you may know and believe that the Father is in Me, and I in Him.”" (v34-38).
Here, Jesus directly quotes Psalm 82:6, a Psalm in which the Congregation of the Mighty really are referred to as "gods", because they are children of the Most High, and have authority to judge the children of Israel. In response to charges of blasphemy, therefore, Jesus effectively says "hey, our own law says these people were gods, how much more of a right do I have to call myself a God, given that I literally proceed from the Father?" And of course, Jesus proved His relationship with the Father through endless streams of miracles, from small "party tricks", like turning water into the world's greatest wine, to major demonstrations of His authority by casting out demons, and ultimately even rising bodily from the grave.
Thus, this application of the word "god" does apply, but it applies to Jesus in a unique way, because He has divinity that no other god has ever had. The judges of Israel didn't have one drop of power in them. They were gods only in the sense that they could legitimately enforce the laws found in the word of God (and Psalm 82 indicates they did a rather awful job of it).
Thus, the concept of the Word merely being "a god" does not work. The only time a non-divine use of the word "god" even comes close to describing Jesus is when a divine spin is put on it. The traditional rendering "and the Word was God" is not only an accurate translation of what the original text says, but it also fits the context of the Bible as a whole. If Jesus is not God in flesh, He was the world's most notorious blasphemer, and Jehovah's Witnesses have a vain faith. If Jesus is God in flesh, He will judge those who reject that fact, and Jehovah's Witnesses have a vain faith. In both scenarios, Jehovah's Witnesses have a vain faith, for which they need to immediately repent.