The best of all is Photoshop ..
If you lean it you can make things that you can't imagine ..
That's one big tool .. Make what you want .. It's WebMaster World ..
The most common is Photoshop. It's like mrgee said. The leading software in Graphic Design. Has a lot of tools and effects all spazzamed into one unique package. It would be the best to use photoshop for designing banners, or etc.
Photoshop is the most widely used graphic editing program. And there are many more like 3DSMax, GIMP, Paint.net, Fireworks etc..
Adobe have recently been updating their software like crazy. Adobe Photoshop CS3 and Adobe Fireworks are both great. There have been some visual updates as well as functionality updates.
In my opinion Photoshop is the best one for graphics design. But people use different software’s like illustrator, image ready, flash and etc... I use Photoshop and flash regularly.
Photoshop is the BEST tool/softwares. Man, you can do so many amazing designs that atleast I have ever imagined of. I have seen some unbelievable photoshopped materials.
I vote for Adobe.