It was about 3 years ago when I discovered you could convert reward points into Xbox gift card and buy games on sale for extremely cheap. Look at the results now.
I did also buy some DLC for games like Zombies maps and soundtracks, so include those on the list too.
Even though they’ve really stifled the amount of points you can earn in a single day, MS Rewards has still given me so much for free. And you know what? I haven’t even played all of these yet.