Evan Dando from the Lemonheads - he has such a versatile and expressive voice, he writes great songs and has a great ear for spotting songs to cover - I like the Gram Parsons and Lucinda Williams songs he sings - I've seen him twice where he's been totally in the zone when it came to his solo acoustic spot - you could hear a pin drop. He struck me as a real pro when it came to performing - I didn't get the feeling he was going through the motions on songs he must have sang a thousand times - he put everything into making them sound fresh and new. He has so much colour in his voice even when he's just talking (yes - he smoked a lot of crack at one time but his voice, against all the odds, has survived in tact) - the recording engineers on his last album said that they had virtually nothing to straightenout usng the autotune technology that is in fairly common use in the studio these days - he has great pitch.
As Finn said Peter Gabriel (for the rich colours he can produce just like Dando) and Kate Bush (been listening to Aerial today in fact) and I even agree on Annie Lennox - she was astounding live.
Daniel Lanois is a favourite - again for the rich tapestry in his voice and lyrics and for his production work - he is a very musical guy in his own right but he also gets such great results from the artists he works with - Dylan, Willie Nelson, Emmylou, U2, Eno, etc.