I've enjoyed exploring the range of usability of each unit type in the game - especially considering everything has one or more specific "counters" defined.
The only unit I've found so far that's a "silver bullet" - one that can do anything in it's setting - is the Corellian Gunship.
Also, standard infantry is greatly underrated, in my opinion, using "Take Cover" to double their longevity. I've used plain stormtroopers in swarms to take down T2-Bs systematically - and by the dozen - and not lose nearly as many of them as I'd expect. And this on hard difficulty. The only thing that wipes them out too fast to deal with (if you get them too close) is artillery.
One of my favorite things is to use only units at the lowest techs (1 or 2) to beat an enemy at tech 5. In other words, I go against the "recommended counters" quite a bit. It's definitely a challenge; the means to defeat many times, but very rewarding when I discover a "new formula" that works well and wasn't known or published before.
In this "counter-heavy" game, it's possible more often than you'd think.