I've always been against stickers/decals on cars...however, in the last year, I've made a few changes to my Cobalt because I just don't care...lol. All on the glass...will get pics of the sides later.
I have Rage Face, ZZP, and a local DIY autoshop logo on one side...the other side is Challenge Accepted. On the back window I put 2 memorial decals...one for my daughter and one for my dad. The ones that say "In Loving Memory" then their name and dates of birth/death. My dad's has a pair of combination wrenches in an X and my daughter's has little feet with a halo.
I have a few ideas for my Sonic when I get it...we'll see if I do anything though, I may want to keep it looking clean (at least for a while).