Atari 2600 + Atari Flash Back 2 fusion.

I took a defective 2600 and merge it with FlashBack 2, in such way that you can still play the FB2 fully, and using the channel 2-3 switch, toggle ON/OFF the FB2 and use real cartridges and controllers as well, all the switches and ports still perform their original functions, also you get composite video out.

http://imgur.com/a/Z7rSw

Also half way through this mod, I actually found what was wrong with the 2600 :-/
Enjoy!

 

That is a nice approach versus adding a cart slot to the side of the Flashback 2 console casing. Plus you gain the composite without needing to do an additional mod. One thing I like about the original 2600 consoles is how solid the cart connector is. Have you noticed much of a loss in sound quality by going the FB2 route versus the original 2600 PCB? Any game carts have issues?

 

There are some carts that do not work, but I think all the ones I own do work, as far as the sound I haven't noticed quality degradation.
I also modded the 7800, 5200, Intellivision, Coleco and TG16 for composite.