What's a material that i can construct a giant egg out of that will shatter?

i think clay, as long as it is thin or glass. to shape glass though you do need a torch or some heat source. even maybe wood if its thin, but i don't think that would give the effect you need. use clay like they use for plates and coffee mugs. or, if you want to be creative, you could actually get a whole bunch or eggs shells up and break them into small pieces (not too small) and glue them together to make a giant egg. hope this helped. good luck!