Gifts to clergy are simply compensation in disguise.
To quote Dan Busby on page 57 of his 2014 Minister's Tax and Financial Guide: "...gifts paid by a church to its minister are typically taxable compensation. This is true if the gift came from the general fund of the church or from an offering in which tax deductible contributions were made to the church for the benefit of the minister."
He goes on to say: "But if the church gives [the pastor] cash or an item that you can easily exchange for cash, such as a gift certificate, the gift is extra compensation regardless of the amount involved."
I recommend that every church purchase Busby's companion sets of Tax and Financial Guides - one for Ministers (see link above) and the other for Churches (2014 Church and Nonprofit Tax and Financial Guide). Cheap and great guidance available on Amazon.