So my kids cut the legs off one of my articulated bugs (https://www.thingiverse.com/thing:2817607) and it actually looked pretty cool. So I modded the bug... into a slug :D
Prints fine hollow, but 100% infill gives it a realistic weight.
Tip for removing from your printer: Stick a putty knife between two body segments and twist it. This should be enough to pop them loose.
UPDATE #1: There is now a file with a slightly rounded tail - safer for youger kids ;)
UPDATE #2: WuffyUnikitty designed a clip-on snail shell for these little guys. Check it out! https://www.thingiverse.com/thing:2899318
Makergeeks Nuclear Green PLA
Clearly, I'm not a hand model.