The Ranger

As you can see, the ranger does not cost any commands to deploy, and also acts without using any commands. Due to these attributes, it is generally a good idea to deploy your ranger on your first turn When deployed during your first turn, the ranger will allow you to gain board control early on while still allowing you to use all of your commands on getting units out.

The ranger is also a great answer to early scout pressure. Since the ranger has 3 commands and 3 range, it can hover outside of the striking range of the scout, get in range, and still have enough actions to both trigger the scouts dodge ability and deal a lethal blow.

The wolf is also a nice add on to the ranger. While it is neither a high damage or high life unit, it can move large distances rapidly and therefore reinforce where needed or threaten weak parts of your opponents army. Like mentioned in Mongolian's post, the ranger can summon infinite wolves if paired with an abjurer.

Last but not least is the ranger's ability to switch to melee mode. Probably one of the more neglected skills in Zatikon, it is definitely very useful in certain instances. At times, someone may have your ranger cornered, or you may be playing with your back to your castle, on top of that they may have parked a unit such as a general 1 space away from your ranger because they did not take the rangers melee skill into account. You may have just attacked the general 3 times with its ranged attack, and only do 3 damage. A much more effective move would be to use 1 action switching to melee, and attack the general twice, doing a total of 6 damage, which is more than enough to kill it. Overall, many seem to hesitate to switch their ranger to melee mode because it uses 1 action, and the ranger can hit and run much more effectively when in ranged mode. With proper support though, such as shield maidens and acolytes, the extra 2 damage that the ranger gains from its melee mode switch give it the power to easily dispatch your opponents hardiest units.

The Assassin

In my opinion, the assassin is one of the most unique units that Zatikon has to offer, its unique method of deployment and its 1 time stun can be used synergistically with a large amount of units.

The assassin is essentially a paper cannon. Its extremely low life and action points coupled with its nonexistent armor make it a sitting duck after deployment. Do not be mistaken though; the "Stuns all surrounding units upon deployment" gives you the opportunity land a large stun on your opponents troops, which allows your units to move up and get in advantageous positions that they otherwise would not be able to get into without taking large amounts of damage. On top of this, if you can keep your assassin alive after deployment, you have the opportunity to take out 2 units within 1 turn.

In order to use the assassin effectively, you must first choose which unit you would like to deploy it on.
I personally prefer riders, due to their ability to close large distances instantly, and deliver an assassin deep into enemy lines. If a great opportunity to use my assassin presents itself, it is best to try to deploy the assassin on the unit that has the opportunity to do so, given the cost of taking that unit off of the battlefield is worth the strategic advantage that is provided by the deployment.

But undoubtedly the hardest, yet most satisfying part of using the assassin comes with where to deploy it.
Clumped up units offer a juicy target for 1 large reason, you can use your opponents stunned units against them. Tightly clumped stunned units create a wall, and if your opponent lacks units with the ability to attack over units and their friendly melee units are far enough away or blocked by the wall, you will be able to use the assassins "Kill enemy unit" ability.

The classic Zatikon standoff.

As you can see, I have used my knight to take out that footman and burn one of the pikeman's action points, I have then moved my footman up to burn the pikeman's second action point.

Boom! Since I was able to peel open a gap in my opponents lines with knight, and burn the pikeman's action points with my knight and my footman, I was able to move my rider in there and deploy the assassin on him. I have sacrificed my knight and my footman to take out his archer and warrior, but I have gained the strategic advantage by retaining my archer.

There are of course many more ways that the assassin can be used. some interesting ideas are to pair it with an abjurer, and recall the assassin upon deployment, which allows you to use the abjurer to act as an enchanter. You can also use the assassin to take out lone units who are attempting to flank.

When your opponent knows you have an assassin, they are much more difficult to use. The best way to incorporate an assassin into your army is to have a large amount of low cost units. When you have only a few high cost units out on the board and an assassin waiting to be used, it is fairly easy for your opponent to see that you are hiding a unit. If you have a large amount of low cost units, sometimes your opponent gets lazy and does not take the time to count the total point value of fielded units, much to his detriment.