Let's state this now: Counter-Strike is awesome. Many an hour has been wasted passed playing the legendary first-person shooter mod for Half-Life, and now even more hours can be whiled away, as the game has come to Android.

Reddit user /u/a1baomarov has posted in /r/Android detailing how to get Counter-Strike working on Android, which involves moving files over from an existing Steam installation, and installing the Xash3D apk.

95%-100% compability with CS1.6.
This requires Xash3D Android >= 0.17.

Install:
1) Install the APK. Install APK with omp postfix if you have multi-core device and noomp if you have single-core device or have problems with omp version.
2) Install the latest Xash3D Android from https://github.com/SDLash3D/xash3d-android-project/releases/latest.
3) Copy cstrike and valve folders from your Steam CS1.6 installation to xash folder on SDCard.
4) Run CS16Client!

Source for instructions: github.com

The APKs, both the omp and noomp versions, are available on GitHub. (Take note that this links to CS1.6 v1.01; an updated bugfix build.)

Screenshot_20160418-232728 Screenshot_20160418-232633

In my tests, the game worked well, with little to no lag on my Nexus 6P. The controls are admittedly fiddly (for example, it took me a few attempts to get through a normal-sized door), but this is to be expected with a game that was never designed with mobile touchscreens in mind. I attempted to take a short video, but unfortunately adb screenrecord doesn't record at a high enough framerate for this to come out well. From reading the reddit thread, I noticed that there doesn't seem to be keyboard/mouse or controller support, but unfortunately I am unable to test this.

If you're so inclined, the instructions are above, or at GitHub, and there's a discussion thread over on /r/Android.