This is a good tutorial by Ryan Boyle for those who want to make pixel art with Adobe Illustrator to have some flexibility with resizing it or perhaps having it printed.
Although this method works fine, I still prefer to create mine in Photoshop with nearest neighbour settings enabled. It’s just my personal preference but I find Illustrator leaves odd stitching artefacts on screen between individual pixels. This can be fixed by merging all the pixels together, but then that means you lose the ability to easily edit your illustration late on.
Never-the-less, it’s a solid tutorial with all the info you will need and I recommend watching and trying the technique out for yourself.