Egg

I made this as a gift box for Easter. Part way though the print I pause it so I can place a gift inside and then I let it finish printing. Then the person it is for has to break it open in order to get the gift. I printed it at .6mm wall thickness so it's easily breakable by hand but should also work with thicker walls it'll just be harder to open.

I used Silk Pla and printed it at
0% infill
.6mm wall thickness
20mm/s outer wall speed (when I printed faster than that there were a couple small holes)
Tree generated support (though I assume most supports will work)

Printing it sideways makes it easier to place items in it since there is a bigger opening but the top 1/4 didn't turn out great because of the overhang. It still completed but could look better.

Be careful with what you place in it and how. The first thing I tried to put in it was a Flexi Turtle but the weight of it caused the wall to move slightly and the print failed. I eventually got it to work by waiting until the print was further along before placing it. I also made one with a stuffed bunny in it. It was light enough and small enough that it didn't cause any issues but I was warned that it could have caught fire if the nozzle got too close