Gunslingers are very peculiar units, designed solely for one purpose – destroying T1 leftovers.
It has some unique attributes that make it perfect for this role:
- Self-repair - it regenerates Hitpoints on the run.
- Fast-learning - it quickly gains experience from its victims and gets buffed with higher range, Hitpoints., creating a snowballing effect
- Repulsive shells - which will keep light units away
However, remember that in its initial form it is not really powerful and may be easily overrun by a big T1 army.
Requires heavy micro to stay out of T1 range.