In service as a sidearm, or everyday carry as a civilian/back-up gun?
In the first case I'd go for a Glock, and my favourite would be 9mm. Glock17.
In the latter case I'd make an odd choise, and pick the 7,65mm Walther PP or PPK.
May sound like a ridicolous and underpowered choice, but fact is that their reliability are well proven for more than half a century, they will fit into holsters and pockets without snagging, can be carried loaded, and the little .32ACP/7,65mm will do the job on close range.
Today we are all Norwegians! Swedish Foreign Minister Carl Bildt. 22. July 2011