Nothing fancy but looks good enough to pass.  Beats the little plastic crap they give you with your shirt.  These things gets lost every few wears so I cant see the reason to splurge.  My everyday suit cufflinks are better investments.

Really, though.  When in a tux, make sure its fitted, Shirt is crisp, shoes are polished, tie is straight and if applicable, put on your best dress watch.  Then, no one is checking out your studs and links