Most of you won't like my first one; but it's got to be Craig Mawlam, the owner of Ionics. I believe he kicked off this WFP malarky with his Reach and Wash. No, he didn't invent it, but he made it mainstream.
No2 is Mike Boxhall; forum owner. Although he didn't invent the interweb, his interweb forum has certainly changed the way many of us operate.
No3 is Jeff Brimble; he came up with the idea of lightweight poles. Prior to him it was all aluminium or fibre-glass. He knacked his back (or something) and came up with the idea of using carp fishing poles with a brush on the end.
No4 is Alex Gardiner; he nicked Jeff's idea, developed it, and made some great poles.
No5 whoever invented the flipfast; a much un-posted about bit of kit, probably because it's simple and works brilliantly.