What is your favourite positive argument for atheism/unbelief?

[Little Rik]

Human life is not a "gift" it is a life. A "gift" is an object. I don't see myself as an object. So a poor African kid whom will die before the age of 5 from starvation in a war torn country is a "gift"? That kind of hell is a "gift" to you? The Syrian kids whom got killed by a gas bomb, that's ok because God gave them life just so they could die a horrible painful death way before they even became adults, you think that is a "gift"? Childhood cancer is a "gift"? 

Silly me, I must have it all wrong, I grew up thinking a "gift" was an object you gave on birthdays and holidays. If you want to use the word "gift" regarding human life, fine, then get me Angelina Jolie and put her under my Christmas Tree, I am sure she wont scoff at that suggestion, I am sure she will say, "Oh what the hell, Brian wants me, I was born a gift so ok, Brian can have me because I am a gift".

I really find it sad to see theists objectify their own lives as if they were mere toys for an invisible man to play with or pass out like a "gift".

Wrong again Brian.  
Your inner feeling get you upset easy well before you consider all situations.
I hope you are not a detective because in this case you would be a total failure.
You jump up to the first option without considering all other options.

Suppose reincarnation exist.
Before you enter an other body you see God and realize how great it is to get close to Him and merge in Him in that ecstatic feeling of total bliss but unfortunately you got a terrible karma so there is no way that you can get any closer to Him unless you reincarnate to extinguish that karma.
At this stage it wouldn't really matter to suffer terribly because at the end you never really die and once you extinguish that bad karma you would be able to reach god and merge in that ocean of total bliss.
In this way God give you the gift to have an other body that will allow you to get rid of your bad karma.
Without that gift you wouldn't have the possibility to reach Him so even a terrible life is still a gift.