FIG. 1 is a perspective view of a mouthguard showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a right side elevational thereof; and,

FIG. 7 is a left side elevational thereof.

The broken line showing is for environmental purposes only and forms no part of the claimed design.