Sure you can be a lawyer and serve God.
http://aclj.org/
As a non-profit organization, the ACLJ does not charge for its services and is dependent upon God and the resources He provides through the time, talent, and gifts of people who share our concerns and desire to protect our religious and constitutional freedoms.
You could also serve as an apologist - defender of the faith - and use your God given skills that way.
http://rzim.org/
Ravi Zacharias International Ministries is a global team of itinerant speakers with offices throughout the world in: the United States, the United Kingdom, Romania, the Middle East, India, Singapore, Hong Kong and Canada. Founded in 1984 by Ravi Zacharias, the vision of RZIM is fourfold:
* Evangelism with a particular focus on skeptics, cultural influencers and critical thinkers
* Apologetics that addresses current issues and the intellectual struggles related to these concerns, and the humanitarian needs of those at risk within a society
* Spiritual Disciplines that focus the mind and heart on the glory of God
* Training that comes alongside the Church or concerned Christians worldwide so that the mandate of I Peter 3:15 might be fulfilled—to set apart Christ in our hearts as Lord and always be prepared to give a reason for the hope that is within us, with gentleness and respect, all for the glory of God.