Give a scenario you would want to change back in time, but it somehow alters the world we live in now. Don't know if this has been done before...
When Richard Nixon announced in his speech that he was resigning effective the next day, I would change it to have him say he would resign in one month. Then he would bark like a dog, quack like a duck and whinny like a horse. And then see how long he could stay president for the next month while continuing to not give a damn about the consequences of his actions.
The time I didn't buy into the IPO of Microsoft The time I didn't buy into the IPO of AOL I'm a spendy guy. That money would have done something for a lot of home, car and bass gear builders. It damnsure would have altered the world I live in now.
I would break up with my ex girlfriend and have a nice summer full of things i would not regret. Also, and get my parents to buy into google stock...
I'd travel back to Germany, 1923, and shank Hitler in jail. Then I'd travel foward 15 - 20 years and buy 5,000 shares of IBM stock.
I'd go back in time to see the folks who conjured up "Care Bears" and "Teletubbies" and convince them the shows wouldn't work. My daughter loves those things. Eeeeck!
buy a copy of Grey's sports almanac, go back in time and give it to my younger self, come back and become rich and rule over hill valley.