Draw wire bounding box corners.

WireBoundCorners.cs

public static void CubeWireCorners(Vector3 center, Vector3 size)
{
    var ext = size * .5f;
    DrawCorner(Matrix4x4.TRS(center - ext, Quaternion.identity, Vector3.one));
    DrawCorner(Matrix4x4.TRS(center + ext, Quaternion.Euler(180f, 90f, 0f), Vector3.one));
    DrawCorner(Matrix4x4.TRS(center + new Vector3(-ext.x, -ext.y,  ext.z), Quaternion.Euler(0f, 90f, 0f), Vector3.one));
    DrawCorner(Matrix4x4.TRS(center + new Vector3(-ext.x,  ext.y,  ext.z), Quaternion.Euler(180f, 0f, 0f), Vector3.one));
    DrawCorner(Matrix4x4.TRS(center + new Vector3(-ext.x,  ext.y, -ext.z), Quaternion.Euler(180f, -90f, 0f), Vector3.one));
    DrawCorner(Matrix4x4.TRS(center + new Vector3( ext.x, -ext.y, -ext.z), Quaternion.Euler(0f, -90f, 0f), Vector3.one));
    DrawCorner(Matrix4x4.TRS(center + new Vector3( ext.x, -ext.y,  ext.z), Quaternion.Euler(0f, 180f, 0f), Vector3.one));
    DrawCorner(Matrix4x4.TRS(center + new Vector3( ext.x,  ext.y, -ext.z), Quaternion.Euler(180f, 180f, 0f), Vector3.one));

    void DrawCorner(Matrix4x4 trs)
    {
        var c = trs.MultiplyPoint3x4(Vector3.zero);
        Handles.DrawLine(c, c + trs.MultiplyVector(Vector3.right) * .2f, LineThickness);
        Handles.DrawLine(c, c + trs.MultiplyVector(Vector3.forward) * .2f, LineThickness);
        Handles.DrawLine(c, c + trs.MultiplyVector(Vector3.up) * .2f, LineThickness);
    }
}