I've always loved Strutter, and I was glad to see it in San Andreas. But when I heard the demo version of it, I enjoyed a lot more. That version had voices that sound more passionate, and it seemed a lot less produced overall. I really like the sound of it. If you want, you can take a listen here:
I was going to lock this unfortunately, seeing as it's quite a narrow window for discussion. However, I decided to just move into the music section and open the floor for demo versions of any track people feel like sharing and talking about. As it stands, I do quite like Kiss. I know they're a bit campy but that's part of their charm.
If we're talking about demo songs in general, Rod Stewart brought out a box set a few years ago which held some rarities and alternate takes of his more popular songs. As solid as "Maggie May" is, I've always been partial to the early version found on that collection. I'd share a video but it's nowhere on YouTube...
Something I did find though was an acoustic demo of "Gold Dust Woman" by Fleetwood Mac, which is found on their remastered deluxe edition of Rumours.