I decided to do a bit of experimenting on reactions of people.
I got the idea because I rarely see people do a sad face expression in real life. Men like to look tough and show no signs of weakness while women try to look charming. This is why it's a bit hard to find someone who actually looks upset.
So what I did was test out a few different facial features and ask for certain things and errands from people that it would be hard for them to give or do.
I tried the great smile expression.
Doesn't work well. People look at me like "who does this guy think he is" and find it easier to refuse my requests as I look quite open.
I tried the very slight smile expression with closed lips.
I've gotten good results with this. People think I'm a good hearted fellow who has no bad intentions and I look a bit submissive.
I tried the neutral face expression. A very dull look.
Not good with this one. People will treat me like the average person. I look like a nobody and I'm not worth their time.
I tried the bored, 'your wasting my time' expression (which is my most used expression)
This gets alright results. What I do is use the expression and if they hesitate giving answer I purposely use a body language expression such as tapping on the table to make them say yes. They get the idea that I'm angry inside and as they hesitate I start physically showing my 'anger' which causes them to quickly say yes.
I tried the slightly angry serious face expression
This works well towards most people. Some people would have a problem thinking "does this guy think he's better than me" but most of the time I guess people are too afraid to annoy and would do the request.
I tried the angry expression
This has a black or white effect. Either the person will totally reject you or do what you want with beautiful results.
I tried the sad expression
This... works wonders. The best expression to use to get what you want. Barely any people use it and if you use it people will get some sort of surprise. People will either feel sorry for you or they will see you as a submissive person and want to help you (they feel they have responsibilty over you).