This is what I am crazy with recently. Been playing this for about a month. Here I would like to share with all of you the soldiers I wish to own one day. Those with really high energy power bar.
1) steam punk lord, energy 500 cost 99750 coins
2) Martian commander, energy 700
3) steam punk commander, energy 600
4) Martian soldier, energy 650
Not all the zombie you can affected and own with the coins some you need to have the toxins. You can purchase the toxins with REAL money and changed the toxins to the coins.
For me, I still prefer playing and accumulating the coins and toxins slowly through out the games.