In your own space, create your own challenge. What’s something you want to see more people doing in fandom? Is there something fun you’ve tried that you think other people would enjoy if they gave it a go? Dare your friends to try it out, and have fun with it.
It's hardly even the 15th anymore, but I've stewed over this all day and haven't come up with anything better than this...
I challenge all of you try creating something you haven't before, or normally wouldn't. Try to break out of your normal box.
Usually write slash? Try femslash, or het. Never tried podficcing? Record a short one, see how you like it. Try making a fanvid, or a fanmix, or a picspam. Try a trope you thought you wouldn't enjoy writing, and find a way to make it work for you. Stretch your boundaries, test your limits, and see what it does for your art.
Chances are it'll at least be fun.