Sírvase

Sírvase
 

In some cases this can be used to mean please. Is it a common usage?

"Servirse" is a polite verb to ask for something formally. I think it's close to "kindly", because we can use "servirse" with "por favor". :D

- Por favor sírvase firmar al calce. (Please kindly put your signature at the bottom.)
- Por medio de la presente, solicito a usted servirse informar a esta oficina sobre las compras realizadas el mes pasado. (By means of this letter, I'm requesting that you kindly inform this office about the acquisitions made last month.)
- Mucho agradeceré que usted se sirva designar a un representante para llevar a cabo las negociaciones pertinentes. (I will be grateful if you kindly appoint an agent to conduct the applicable negociations.)

Also, take a look here. ;)