I've seen this come up on a few online groups recently: people wondering if there are any charts that use all of the DMC (solid) colors. To my knowledge, there are 2.
The first is Floral Finesse. I've listed this one first for two reasons: I'm working on it and it hasn't been updated with new colors. This one was charted for the DMC 250th anniversary and used every solid color available at that time. That means it uses 390 colors. Here's my progress on it so far:
The second one was originally charted at the same time and used 390 colors. It has since been updated to be 447 colors (it doesn't used the 7 colors that were "merged/discontinued" in European markets). This one is by Joan Elliott and it's the Angel of Cross Stitch. The only reason that I won't stitch this is because I don't care for artistic representations of angel (fairies, elves, etc.). Yes, I do believe in angels, I just don't like art of them. :-)
I haven't heard of any chart that uses more than the Angel of Cross Stitch. If anyone else knows of charts with over 400 colors, I will happily update this post to include them. Just leave a message in the comments.