There wasn't any single part that made it bettar than everything else. But the handling of the models with stiffer suspension (1991-1994 Lumina Z34, 1995-1999 Monte Carlo Z34, and 1997-1999 Lumina LTZ) combined with the V6 power, generally awesome exhaust notes, comfy interiors, and responsive steering make the performance models a JOY to drive.
If you wanted something to ogle over for being unusual, look at the LQ1 engine. pushrod engine block, a timing chain, a timing belt, DOHC heads, and 24 valves all on a 60 degree V6 block.