Reaper is a general purpose raider with significant armor and a decent plasma weapon. It can easily outrange and destroy most T1 units. This is the main and most numerous constituent of your T2 vehicle forces. Build them in huge numbers to overpower your enemy with sheer force. It is cheaper and more armored than its ARM counterpart (Bulldog) but it deals less damage and offers shorter range.
Combine them with Banishers to make a good counter to Bulldogs.