Mirror, Mirror
For close buddies, your child can make a Valentine keepsake. Round up any small pocket mirrors (for some reason, we always seem to have extras of these.) Most craft stores also carry small mirrors in various shapes including hearts. Use leftover nail polish to decorate the mirrors with hearts, squiggly lines, or dots. This same decorating technique could be used on any leftover tiles from various redecorating/remodeling projects. For younger kids for whom breakable Valentines would be a shaky proposition, use aluminum foil glued onto paper or try some metallic craft paper.