Re: I'm touched by the weirdness of this request...
I wouldn't start with Unseen Academicals or Raising Steam, two of the last Discworld series as I'm not sure they are as good as the others. Felt like he was losing his bite, particularly in Raising Steam *ducks and runs for cover*
Hard to pick a favourite, but I would probably start with Guards Guards and then follow the Commader Vimes focused ones for a bit.