I guess the artist that people generally expect me least likely to listen to (being mostly an 80s/90s metal-head) is Lonnie Donegan.
That guy just rocked, plain and simple.
I managed to see him at Guilfest in 2000 (took my dad along to see Van Morrison) where, at the age of 69 he rocked harder than any of the supposed "headlining acts" on the main stage.