For Orchestral/Grand Scale (but not the typical warhorses):
Jean Sibelius - Symphony No. 7 in C major, Op. 105: Unlike many symphonies, this one is in a single, continuous movement. It's incredibly powerful, atmospheric, and builds to a majestic, unforgettable climax. It shows Sibelius's mastery of orchestral color and form.
Antonín Dvořák - Slavonic Dances, Op. 46 (e.g., No. 2 in E minor, No. 8 in G minor): While some are somewhat known, the full set of Slavonic Dances (Op. 46 and Op. 72) is a treasure trove of vibrant, folk-inspired orchestral pieces. They're joyful, melancholic, and incredibly rhythmic, celebrating Slavic culture.
Alexander Borodin - Polovtsian Dances from "Prince Igor": While the main theme is used in popular culture ("Stranger in Paradise"), the full orchestral suite is lush, exotic, and incredibly exciting. It's truly a spectacle of sound.
For Chamber/Intimate Settings:
Gabriel Fauré - Pavane, Op. 50: A wonderfully elegant, refined, and melancholic piece. It exists in both orchestral and piano versions, but the chamber version (for small orchestra or even just piano) is exquisitely delicate. Perfect for a quiet, reflective mood.
Luigi Boccherini - Minuet from String Quintet in E major, Op. 11 No. 5: While the Minuet is fairly famous, Boccherini wrote an incredible amount of charming and graceful chamber music, especially for strings. His works are often overlooked in favor of Mozart or Haydn, but full of wit and beauty.