Dollar Shave Club is perhaps the archetypal challenger brand. In 2012, its cheeky viral video poked fun at shaving giants like Gillette and Schick for producing over-engineered razors. Although Gillette is hitting back with a series of confrontational tweets, the campaign is backfiring.

For many men, shaving is one of life's necessities, with 75% of American men shaving daily. But a marketing war between Gillette and Schick has created a razor market that's expensive and over-engineered. Selling cheaper, back-to-basics razors, can Harry's offer an alternative?

While 76% of men feel pressure to look good, seeing a bloke stroll into a brow bar or waxing salon could still raise an untamed brow or two. But London-based The Beauty Block has located both above A Wanted Man – a male-centric canteen that acts as an acceptable gateway to grooming.

In his 2015 book Gamechangers, innovation expert Peter Fisk provides 100 case studies of businesses that have won the game, changed the game or even invented their own games via new strategies and innovations – from global giants to small start-ups. So what makes a game changer?