The power of Town Meeting - sometimes through it's Advisory Committee:

The town meeting can have a great deal of control over department heads. The town meeting can, for example, investigate town problems or administration through its advisory committee, other standing committees or special ad hoc committees. On the basis of findings and recommendations by such committees, or on the petition of ten or more local voters, the town meeting may adopt resolutions and bylaws establishing new town policies or initiating new programs [G.L. c. 39, §10]. The town meeting can also, within certain limits, reorganize town agencies and control development in the town. The most important power of town meeting is the power of the purse. By appropriating or withholding funds, the town meeting can force, prevent or influence actions by town officials and departments.

The above can be found in the latest copy of selectmen handbook.