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Most also offer nice animation tools such as looping your animation in real time allowing for effective tweaking. Even other simple niceties like they are always hard edged, always scale with a nearest neighbor algorithm, having both the right and left mouse button be full fledged tools, etc.
The canonical tool was Deluxe Paint on the Amiga, and most tools still around today emulate it at least to some degree.
I don't think Photoshop does this (I haven't used it for several versions and my art days are more or less over) but the above has made me forever slightly wary of attempting pixel art in a package primarily sold for photo editing.
Plus, Photoshop is expensive. If you have it anyway and it works for you, that's cool. If you're looking to install something just to make pixel art, you're spending a lot of money on a lot of features which are irrelevant to you and may make it harder to find the functions you actually need.
I'm surprised he mentioned Photoshop. There are many dedicated pixel art programs that are far better for the task such as [Pixen][0], Graphics Gale[1], the new Pyxel Edit[2] and my own LoveToPixel[3] (done in HTML5 Canvas)
[0]https://github.com/Pixen/Pixen [1]http://www.humanbalance.net/gale/us/ [2]http://pyxeledit.com/ [3]https://github.com/city41/LoveToPixel