There's something to be said for consistency, no?
One of my favorite "standbys" is a well-designed set of black letter stickers. Like a little black dress, you can never go wrong with a black alphabet sticker title. I have a few that I use regularly, including this one from Making Memories and this one from Scenic Route. Notice that both sets offer *all* letters of the alphabet, including X. :)
Does anyone need or want any clear buttons? I have too many and need to share. Let me know.