Judges 6:15 Gideon said to him, "Me, my master? How and with what could I ever save Israel? Look at me. My clan's the weakest in Manasseh and I'm the runt of the litter."

Isaiah 40:29 He gives power to the faint, and to him who has no might he increases strength.

God called Gideon to save Israel from the Midianites. Gideon told God that he couldn't because his clan was the weakest and he was the smallest of the clan. It's kind of funny how we humans think we need to tell God something He already knows. God knew who and what Gideon was. Most likely God picked Gideon because he was small and from the weakest clan. God has a tendency to pick the weak, or the least likely person to do His work.

Moses was hiding out with the sheep and had speech problems. God chose him to lead Israel out of Egypt.

Esther was an orphan girl and she was chosen to save Israel.

Samuel was a little boy when God called him to give him a message for Eli the priest and then started Samuel on the road to become a prophet of God.

David was a boy when God worked through him to kill Goliath.

Joash was only 7 years old when he became king and started repairing the temple.

The lessons that came out of Job's suffering continues to help people to this day.

Samson had to be brought to his knees and made the weakest before God could use Him against the Philistines.

Paul, was temporarily blinded and left with a physical problem before He would accept Jesus as His Savior and go on to lead the early Christians.

No one is too old, too young, too ill, too messed up, too anything for God to be able to use them. There is not one person who cannot be used by God except the person who doesn't want to be used by Him. All He needs is an invitation from us to come in and start working through us. Our job is to be available for Him to use us to do whatever it is He needs us to, at whatever pace He wants us too, and with whatever results He is wanting. We don't need to pick the job, He will place the burden on our hearts. We don't need to force the results or try to speed things up. We just need to be ready, willing, and in close communication with God. The rest is up to Him to take care of.

For more on this topic:
Serving God in Our Own Way
Wonderfully Made
God Doesn't Make Junk
He Will Finish the Work in You