This is a wonderful thread! I really like seeing what artists have inspired other people, and it gives us the opportunity to share a little of our enthusiasm for the artists we love so much.
Other than the first three these are in no particular order I guess.
Akira Toriyama's work especially through his run on Dragon Ball. Whether it's earlier, more detailed work or his later, more economically streamlined work, he always inspires me. He is my favorite artist of all time, but I'm sure he gets an unfair advantage for being able to take me back to feeling like a care free little kid. Plus he wrote and drew all of Dragon Ball with only one or two assistants at a pace of roughly fifteen pages a week while designing characters and environments for movies, shows, games, etc. for a span of about ten years. It's no wonder he got burnt out by the end of it!
Next up is the consummate professional, Joe Kubert. This man is one of the best artists U.S. comics have ever showcased, if not the best in my opinion. I think he was head and shoulders above his peers in the 60's and is still producing top quality work now that the rest of them are mostly retired.
Michelangelo. I really probably don't need to say anything about him. His work is put lightly as legendary. I enjoy looking at his sketches even more than his sculptures and paintings.
Olivier Coipel is one of my favorite artists in comics at the moment (though it's been a long moment). I try to emulate his use of blacks and cross hatching. He also delivers a nice balance of detail and economy of line.
N.C. Wyeth illustrated books like The Adventures of Robin Hood and Treasure Island. His work is always dramatic and full of life.
J.H. Williams III is the best artist out there when it comes to panel layouts. I don't think anyone even comes close. He showcases brilliant design sensibilities in his comics yet everything is still clear and easy to read. He is my other favorite artist in comics today.
Alphonse Mucha was a Czech art nouveau painter. His illustrations of women are wonderfully designed, graceful and packed with detail.
Stuart Immonen is an inspiration to me personally as well as artistically. He's self taught like I am and he's still one of the best artists out there.
Masashi Kishimoto draws the best fight scenes I've ever seen in any comic. His art in Naruto can be some what inconsistent at times, but when he's on he is on. Those fight scenes are just insane though. This is his Dragon Ball tribute. I included it just because I love Dragon Ball and I think his style really works well with the characters.
Takehiko Inoue is best known for his series, Slam Dunk. I think his art was okay at the start, but it was still too reminiscent of City Hunter which he was an assistant on. Once he hit his stride and let his art develop into his own style he blew me away. He's a fantastic artist and I wish I could draw just like him.
The variety of Street Fighter artists, but the primary SF3 designer specifically. Collectively the Capcom crew is just full of amazing artists. I wish they would draw comics!