I think it's important, instead of taking ONE verse, to look at the entire passage in context:
1 Timothy 2:1-6
I urge, then, first of all, that requests, prayers, intercession and thanksgiving be made for everyone for kings and all those in authority, that we may live peaceful and quiet lives in all godliness and holiness. This is good, and pleases God our Savior, who wants all men to be saved and to come to a knowledge of the truth. For there is one God and one mediator between God and men, the man Christ Jesus, who gave himself as a ransom for all menthe testimony given in its proper time.
Clearly we see that praying for others on their behalf is good and pleasing to God. It does not take away his role as the one mediator in any way.
If one is going to say that Christ is the only mediator and we should "pray only to Jesus", then one should also not ask others to pray for them... lest they be contradicting themselves. One must understand what it means for Christ to be the one mediator before they throw the argument on the table. Of course, we should also pray to Jesus but even Jesus himself encouraged us to pray for others (Matt. 5:44).
What follows this explanation is usually, "Well, those in heaven are dead. They can't hear us."
Is this true?
Revelation 5:8 says, "And when he had taken it, the four living creatures and the twenty-four elders fell down before the Lamb. Each one had a harp and they were holding golden bowls full of incense, which are the prayers of the saints." (See also, Rev. 8:3-4)
Here we see 24 elders (humans) in heaven offering the prayers of the saints. In order for them to offer the prayers of the saints, they must know what these prayers are. Prayers are not physical elements and must be offered mentally.... And, on another note, those in heaven, are only dead in earthly body. Their souls remain alive in Christ. There is only ONE body of Christ (Ephesians 4:4) and those who pass on to heaven do not cease being a member of that body. In fact, they are perfectly united to Christ! They are made righteous and the prayers of the righteous are "powerful and effective" (James 5:16). Would God not permit those in heaven to pray for us when their prayers for others are pleasing, powerful and effective?
In addition to Rev 5:8, we see prayers to angels in Psalms 103...
20 Praise the LORD, you his angels,
you mighty ones who do his bidding,
who obey his word.
21 Praise the LORD, all his heavenly hosts,
you his servants who do his will.
Clearly, the Bible directs us to pray to those in heaven through this passage and ones like it.
The bottom line is, we must take all of Scripture into account when we discern what a passage means. Christ as the one mediator does not mean that others cannot pray for us, including those in heaven. Scripture tells us that those in heaven can hear our prayers and that they offer them to God for us. This is part of the beauty of the Christian faith: that we are not disconnected from other parts of the body of Christ but that, through the power of God, they are able to intercede for us! This does not limit God's role but magnifies it! It is only by His awesome power that we are able to remain in communion with ALL the members of His Body. He IS, indeed, the One Mediator between God and man. This role is specifically what allows us to intercede for one another and for those in heaven to intercede for us!
