My nominations would be :
Richard Noble (Thrust 2 and SSC - awesome),
Crick'n'Watson (discovered the structure of DNA)
Frank Whittle (invented the jet engine - probably)
Alan Turing (came up with the concept of the finite state machine, father of the modern computer)
However, if you ask the younger generation, you're likely to come up with
Posh
Becks
Jordan (2 peaks required)
On the other hand, if any form of government sponsorship, permission, or other involvement was required, then I'm pretty sure that Tony Blair's face would end up on it. 4 times.
That's not an expression of preference, btw.