My favorite T configurations generally take a new road to the same place the Prime went by using some newer tech. The Mad Dog T is the most elegant example of this. But since the Mad Dog is rightly getting a lot of recognition, I'll show some love for a creative configuration given to a mech that was never conventionally good and was always going to be hamstrung by the WYSIWYG parameters: the Crossbow.
The Crossbow T, despite the valid complaints that might be lodged against it, manages to be a fun and useable platform in-game and quite nifty from a design perspective. Two ER large lasers as the only non-one-shot weapon may not be an efficient use of 65 ton mech, but that sort of firepower is hardly ineffective. And the sheer quantity of one-shot missiles means you can still knock out a couple of damaged mechs or clear out the PBI or vehicles holding your future sniper’s nest. Considering the limitations of the chassis, making a useable T configuration was always going to be a tall order. But I’d call an energy-focused Crossbow that can put 20 points of damage out to 25 hexes (and can even do so while running without immediately feeling the heat) while still being able to launch 20 missiles per arm a creative coup.
My least favorite T configurations are the ones that take established designs and swap in new versions of classic weapons. The Huntsman is probably the best illustration of a dubious T upgrade for modern times, but I don’t care for the Dire Wolf T either. I think those “kitchen sink” mechs were always going to be tough to make a T configuration that manages to be fresh, good, and WYSIWYG.