Last year Bill Gates brought out Slash of Guns N' Roses as his ringer in an on-stage Guitar Hero competition against Microsoft exec Robbie Bach. (Microsoft photo)

Apart from which new technologies will be unveiled, the big question at the Consumer Electronics Show each year is which aging celebrity Microsoft will trot out in an attempt to add some star power to its keynote. With Bill Gates now absent, and CEO Steve Ballmer appearing in his place, it would be surprising if the company didn't do the same this year.

So who will it be? To help inform your speculation, here's a look back at some of the celebs Microsoft brought on stage at the show in the past.

2001: Actor/wrestler Duane "The Rock" Johnson joins Gates on stage with the newly unveiled Xbox, resulting in scripted banter such as this ...

THE ROCK: Both The Rock and Bill Gates are best selling authors. And both The Rock and Bill Gates are known worldwide for their vast array of catch phrases. For example, The Rock has, know your role and shut your mouth, lay it the smack it down, and of course, the world renowned, if you smell what The Rock is cooking. And, Bill Gates, you have some pretty cool catch phrases, as well. What are some of your favorites?

MR. GATES: My favorite is probably writing hardcore C to create slick, tight code.

2004: Jay Leno, most famous in Microsoft circles for his role at the Windows 95 launch, resurfaces at CES to help Gates unveil products including the company's latest MSN Broadband version.

2005: Another NBC late-night host, Conan O'Brien, appears at CES with Gates to do the keynote in a talk-show format. But the evening was most memorable for a recurring glitch during one of the product demos.

2006: Microsoft brought out boxing sportscaster Al Bernstein to call a video-game bout between Gates and Ballmer. Hate to spoil the secret, but the Microsoft execs weren't actually controlling those fighters.

(Photo credits: Microsoft)