Oh wow, this thread is great! We only have a pretty basic bag of tricks, but I am constantly on the look out for inspiration, so this is great.
The only ideas I can really suggest are shaping exercises and rear end awareness.
Shaping exercises such as getting into boxes, starting with big boxes and marking/rewarding for little sucesses and building up until they know to stand or sit in the box. We cheated, Abby prefers to sit.
Then work your way up to different size boxes and different shapes or whatever you wish.
Rear-end awareness... Front paws on box and encourage her to use her back legs to go around the box slowly. Eventually, Abby learnt to go left or right by following my feet. Another one is our 'go around' trick. By luring first, you can teach your dog to go around any object, eventually both ways. You can then try and increase the distance (we are still doing this).
I agree that the sneeze trick is fun! I marked Abby sneezing one day and I was suprised with how quickly she picked it up. I am still doing the transition from her 'offering' the trick to actually performing it on command, but she loves it! Good luck with it!