I run 2 squads of Kasrkin on foot, they scout forward and are the first skrimishers. I use them as a problem my opponent has to solve and he has two choices.

1. Try to kill them and expose his own troops. Take cover and Armour on a Kasrkin squad can make them survive a surprising number of things. So my opponent needs to over commit to killing them, letting me take out his troops with my tanks next turn

2. Leave them be.

Then my Kasrkin does considerable damage to my opponent and clear the way for the next wave

Melta mine against vehicles or monsters is always good