Europe

Easy: [50cl Paulaner][1] Weissbier Kristall (and similar bottles from same brewery). Soak in water and just remove some "glue lines" with a dish brush. Very easy, actually came off while cooling in the ocean. 

Hard: [33cl Heineken][2] with transparent plastic label (might be Sweden only). The label and glue are a nightmare to remove. 

  [1]: http://www.spendrups.se/upload/ProductDB/%C3%96l/Paulaner_50eg_hwk_detalj.jpg
  [2]: http://www.spendrups.se/upload/ProductDB/%C3%96l/heineken_detaljbild.jpg