Insertions in the New Testament

Mark16:9-20
If you look at these verses, right before the verses start there is a bracketed comment.
"[The earliest manuscripts and some other ancient witnesses do not have verses 9–20.] "
The entire information on Mark 16 can be found at http://en.wikipedia.org/wiki/Mark_16
Looking at the info Here you will see the conclusion is that this ending is an insertion at a much later date.
   This insertion is pretty significant due to the fact it is a resurrection account. Marks ending in verse 8 has the women leaving and they tell nobody in fear.... the end. Of course the scribes who are copying this can't believe it ends this way and insert their own ending.  
   If you read each Gospel alone, as it is written by that author, you will get Mark's story. If you read them all one after another you will find that they all blend in. Here is where today's Christians read all four and combine events in each Gospel into one, this is considered making you own Gospel. Each Gospel is its own separate account. Mark's Gospel has no beginning(birth narrative) and no end(resurrection narrative). It is an account of a very human man doing the work of God, performing healing in God's name, gets crucified, buried and the end.

Luke 22:43-44 found in the story of Christ's agony at Gethsemane in Luke 22:39-46
Here we have another insertion about Jesus shedding sweat drops of blood. The doctrinal views that Jesus suffered other than in the crucifixion are supported by these verses. Agony at Gethsemane here you can see the modern scholars pointing out that it is an insertion and the reasons/motives for the insertion.

John 7:53-8:11
The very popular story of the adulterous woman. Jesus enters the temple courts and finds them condemning a woman accused of adultery. Before they are about to stone her he writes on the ground saying let the one who hasn't sinned throw the 1st stone.
"[The earliest manuscripts and many other ancient witnesses do not have John 7:53—8:11. A few manuscripts include these verses, wholly or in part, after John 7:36, John 21:25, Luke 21:38 or Luke 24:53.]"
Here is some Historical criticism of this text Here
Some significance here in this story would insinuate that Jesus would be the only one who hasn't sinned and opts to not throw the stone and tell her to go and live a life without sin.

John 5:4  from the Healing at the Pool in John 5:1-14
Some manuscripts include here, wholly or in part, "paralyzed—and they waited for the moving of the waters. ⁴ From time to time an angel of the Lord would come down and stir up the waters. The first one into the pool after each such disturbance would be cured of whatever disease they had."
http://en.wikipedia.org/wiki/John_5#Interpolation  It would appear here we have another insertion where every time an angel comes down and stirs the water, the first one who gets in the pool would be healed.

The single most controversial verse that does not appear in the oldest and most reliable Greek manuscripts is 1 John 5:7-8 The verse is the only verse in the entire Bible that explicitly acknowledges the doctrine of the Trinity. Now if you take a close look at the footnote, this verse is not seen in any manuscript predating the 14th century. More reading on the subject can be found Here and an extension reading with theories and evidence Comma_Johanneum
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These few I linked here are just some of the insertions/interpolations that appear in the New Testament. Even though some of these may or may not be significant in Christian doctrines, the fact that they exist is evidence that the Bible is not 100% accurate and without errors, is significant.

Summary of the Facts:
* There are verses in the Bible that have been altered, inserted, or omitted by ancient scribes.
* Clear evidence that the Bible is not 100% God's Word is given in these insertions.