And Bible and MySword have the most free resources available by far, I think. (Think of e-Sword or Online Bible for Android and you'll get the idea.) But neither are as user friendly as Olive Tree, Cadre Bible, Pocket Bible (Laridian) Tecarta and maybe a few others, not to mention Logos. All those I just named have a handful of free resources but you have to pay for many public domain resources that are free with And Bible and MySword. And Bible also has the ESV if you use that.
One that I used to look up things quickly on BlackBerry (I think) and now on Android is called Quick Bible. It is just what it says it is-a Bible (mostly public domain ones) and a program that operates very quickly. (By contrast, for all its merits, I've always found Olive Tree to be quite slow). If I want to look up something quickly I open that ome as often as any other. Part of that is because the same developer has a "Morning and Evening" app and the scripture links open in that app.
The difference between all of these and Bible Gateway is that the latter only works if you are online whereas you download files with the others (thus taking up more space on your phone, and some take up more space than others) and it works offline. There is an app called Live Bible that works offline and pulls material from Bible Gateway. I haven't played around with it much but I don't think you can download everything.
Another one that works mainly online that a lot of people like is YouVersion.
If you are a Piper fan, Cross Connect Bible links a lot (all?) of his sermons to the appropriate passages.