For me -
Liszt Sonata has been a brilliant benchmark, love comparing recordings.
Chopin etudes, for technical skill, it’s my go-to crystalline comparison.
Randomly Schumann’s Carnaval - A brilliant way to hear how each different pianist can shift character.
Scriabin sonata No4 - To me it’s one of the best pieces to hear a pianist in dynamic repeated-chordal passages.
Cliche but Rach 3 - hackneyed but I love hearing a fresh interpretation that reignites my love for it.