I've always liked Williams' 1993 pinball machine Bram Stoker's Dracula pinball machine. That's truly a testament to how cool its gameplay is because I don't particularly like vampires in general or that movie in particular. How cool is the game's Mist Multiball mode, where the a pinball seemingly floats across the playfield, starting multiball when you hit it with another ball.
A Pinside member named "November" is working on an elaborate new mod that replaces BSD's static coffin decoration. It pops open at certain points of the game and the actual bat creature from the movie pops out, flanked by realistic-looking burning torches. Check this thing out! It is not yet complete, but after spending a long time creating it the mod is close. The creator stated that once it's done he will consider producing additional examples to sell to other Dracula owners.
3D printing has really ushered in an era where some really cool mods for pinball machines can be produced by members of the community. You all are making me want to buy a printer to play around with.