Avenir Heavy  Suggested by SashiX 


Keep Calm  Suggested by fonatica 
Keep Calm And Type On  Suggested by marijnkampf 

@Rodolphe: it's not the official Keep Calm font

thanks to the two

Alternatively you could use the Keep Calm and Type On font from http://www.keepcalmstudio.com/font. It has both the crown and the upside down crown included. I've specifically designed it to match the font from the original Keep Calm poster.