[DustyPorViva]

I use MSPaint, personally. It's not that advanced(lacks layers and crap), but it gets the job done. I have Photoshop but it's just not fit for pixel art. I heard really great things about Promotion for pixel art(many people at pixelation use it, and those that praise it do pixel work for money), but it costs. If you're looking to get serious, I guess you can look into that.