if that guitar is worth more than a nominal amount (se below) say like $25(?) the church should have included it on your W-2 as compensation. If it's worth a lot more the church should issue a corrected w-2.
An exception to the general rule of taxing incentives and rewards is de minimis benefits. These benefits are so low in value and frequency that having to account for them would be unreasonable or impractical. For example, office snacks, use of the company copy machine, holiday gifts, or occasional meal money for working overtime.
