There is a self-regulating auto-transformer - called a Ferroresonant Transformer, but they only cover a modest voltage range. Used to protect equipment from brown-outs and voltage spikes they are the closest to what you are looking for.

http://www.ustpower.com/comparing-automatic-voltage-regulation-technologies/avr-guide-ferroresonant-transformer-type-voltage-regulator/

Otherwise you need to make up a special AC to AC supply that takes 100 to 240VAC and rectifies it, passes it through regulation (switching supply is best) then use that regulated DC to drive an inverter to regain your regulated 115VAC @ 60hz.

Several problems, most of which are related to the instantaneous voltage drops when the flippers are activated will probably be quite noticeable unless you can build some real current capabilities into this device.

It is doable, but will take some design time, and hefty parts - you need around 500VA I would think for a WPC game.

Something like this for the inverter:

http://www.kgselectronics.com/products/static-inverters-60hz-tsod/ss50.html

The primary input could be a computer switching supply that automatically handles 100 to 240VAC input - you can get quite a bit of 12VDC out of these animals!

This is a bit too feeble:

http://www.zzounds.com/item--HOSADC477

Need to spend some time (and money) to get it right, but doable! The input side would accept the various computer power cords for each country. Output would be 115VAC @ 60hz @ 5A or so to start. Note that 5A at 120V is 50A at 12V...24V to 48V would be easier to work with if suitable inverters exist - 1/2 to 1/4 the current, easier to wire up, etc. However then off the shelf parts might be trickier...(read more expen$ive).

John :-#)#