I have a mouse... standard rolly-on-the-desk kind XP I don't do digital art (besides spritework sometimes) because the only art program I have is MS Paint So really it doesn't matter too much for me anyway
Logitech optical mouse, specifically this one [link] but I hate it. >_< I like using ball mouses better. Less jumpy, as long as you keep it clean, and you don't have to recharge them. Never used a tablet before.
I use a tablet of Genius,but an optical mouse came out with it,so somethings like adding letters or selecting I do it with the mouse and the artistic things like painting and drawing I do them with the tablet.
I use a mouse most often, unfortunately. I have a wacom tablet, but I can't use it. Reason being, it's 4:3 and my resolution is 16:10 so it distorts everything I draw >.< . Really, the best way for me to be able to use a tablet is if it was the screen... which they have... but crazy expensive >.<;;;;; . I do use it on occasion when I'm doing something abstract or something in Photoshop, though. Just not in Illustrator. I tend to work better in Illustrator with a mouse for some reason.
Oh yeah, the mouse is a Logitech Click! Optical Mouse. Very comfy. I didn't need that fourth button, but I found a great use for it (cycle through windows). I may be a mac user, but I can't live without a mouse that has at least 2 buttons and a scroll wheel ^^
I don't really goof around with the computer much to make art, but when I do try to do something I use the mouse. I find it works better for me. I played with a tablet once. I just couldn't get it to work for me. I should try it again...
I have to use a mouse, because I don't have a tablet yet. They're really expensive. The one I want (the Wacom Intuous3) is 300+.
Someday I'll get one.
The mouse I have now though isn't shabby. It has a trackball which is guided by my fingertips, and its very accurate and precise. Its not like holding a digitial pen for a tablet, but its probably the next best thing.
Because most of my art is all drawn traditionally however with paper and pencils and then colored and scanned in, or scanned in and then colored, the digital aspect of my art doesn't play as much a role as it will. The more and more I use programs like painter, etc, the more of a need there will be for the mouse and then eventually the tablet.
This mouse though is very versital, and I use it for everything, including web browsing. Because its a trackball, the mouse doesn't need to move or have a mouse pad.
I have used a combination of both over the years. It depends on what you want to do. I use a mouse for colouring and altering of my ink drawings, while I use a tablet for my animation, and for my old attempts at some fan art, which didn't work for me in the end.