Organisms that contain rare chemical elements
All the elements you mention (B, Fl, Si, V, Cr, Se and Ti) are listed as (probable) essential trace elements in humans by the World Health Organization. The WHO document "Trace elements in human nutrition and health" mentions a host of studies addressing the functions of these elements in species ranging from bacteria and plants to primates. The following list provides some of the functions these trace elements have in humans:


Boron - essential for cell membrane characteristics and transmembrane signaling (Nielsen, 1991);
Fluoride - necessary for the prevention of caries and it is associated with bone health (WHO);
Silicium - probably essential for healthy connective tissue and bone (WHO);
Vanadium - possible role as an enzyme cofactor and in hormone, glucose, lipid, bone and tooth metabolism (WHO).
Chromium - essential trace element that potentiates insulin action and thus
influences carbohydrate, lipid and protein metabolism (WHO);
Selenium - essential component of one of the antioxidant defense systems of the body (WHO);
Tin - expected to have a function in the tertiary structure of proteins (WHO).


References
Nielsen, FASEB 1991; 5: 2661-7
WHO, Trace elements in human nutrition and health 1991