God spoke to Moses through a burning bush. Think about it. First of all it's God speaking. You would think that he would just automatically believe that what He says is right and true. The Lord also gave him some miraculous signs to demonstrate Himself to him — He turned a rod in to a snake and back again. He also made a healthy hand leprous and then healthy again. You would think that would be enough. Not for Moses:
Then Moses said to the LORD, "O my Lord, I am not eloquent, neither before nor since You have spoken to Your servant; but I am slow of speech and slow of tongue" (Exodus 4:10 NKJV).
Moses felt so inadequate. He really wanted to say to God, "Send someone else." His words came out this way:
O my Lord, please send by the hand of whomever else You may send (Exodus 4:13).
God was a bit angry with him, but told him that Aaron would be along to help. God is so patient with us as we struggle with our inadequacy and fear.
God was looking for someone to deliver the people of Israel again, years later, and chose Gideon.
And the Angel of the LORD appeared to him, and said to him, "The LORD is with you, you mighty man of valor!" (Judges 6:12).
God wanted Gideon to know that He was sending him out with power:
Then the LORD turned to him and said, "Go in this might of yours, and you shall save Israel from the hand of the Midianites. Have I not sent you?" (Judges 6:14).
O my Lord, how can I save Israel? Indeed my clan is the weakest in Manasseh, and I am the least in my father's house (Judges 6:15).
Gideon was so unsure and insecure that he had God make a fleece wet, then dry, and so on. God was so patient with Gideon to help him with his insecurity.
God does use unlikely people. Look at the 12 that Jesus picked to be His apostles. Look at other leaders throughout Scripture. All of this should be comforting to you and me. If we feel inadequate, that is good, because we will be totally dependent on God and God will get all the glory for what He is able to do through folks like us.