The DGT 2010 is the standard but is often upgraded to the DGT XL for top tournaments so that the clock can be paired with the DGT sensor board and pieces (which is what is used almost exclusively in top level tournaments and matches).
I can't remember the last time I saw a pic of anyone in the top twenty five in the world using something other than a DGT XL clock and the DGT sensor board.
Nice. Thanks! I guess I'll get one of those then.
Also, in case you've got some extra money laying around (and who doesn't these days, am I right?) and want to go all out, it's the walnut board with 'timeless' pieces from DGT that are almost always used in the big tourneys and matches. Sometimes you'll see the 'classic' pieces, but it's almost always the 'timeless'.
http://digitalgametechnology.com/site/index.php/Electronic-Boards/dgt-e-boards-usb-walnut-with-pieces.html
I want to buy myself a chess clock, so here's a simple question: is there an official clock used in FIDE and/or USCF tournaments?
Oh, and by the way: is there an official combo of board and pieces used in these tournaments?