DDROAD
Code is for the Marvel store but it will go onto your Comixology account if you link them.
You can also get free first issues of Ms. Marvel, Nova, All-New X-Men, and New Warriors using the code "teen" here: http://comicstore.marvel.com/All-New-Marvel-Now-Teen-Heroes/…
I didn't want to lead with this as people are reporting the code is a little dysfunctional. It sometimes takes several goes to get it to work. The above code worked perfectly first time I tried it though.
Worked fine first try for me, thanks OP