If you see base on promotion , you might say Iphone is the world best selling mobile phone. You will be surprised that the model which still holding the title until now is Nokia 1100.

The Nokia 1100 is a durable ultrabasic GSM mobile phone produced by Nokia with a 96 x 65 monochrome screen. It is targeted towards developing countries and users who do not require advanced features beyond making calls and SMS text messages, alarm clock, reminders, etc.

Over 200 million Nokia 1100 cellphones have been sold since its launch in late 2003, making it the world’s best selling phone handset, as well as the best selling consumer electronics device in the world, beating Sony’s Playstation 2 (125 million), Apple’s iPod (170 million), Motorola’s RAZR (100 million), and LG’s Chocolate (10 million).

Via Wikipedia