Magus420
Smash Master
Sheik's up-B explosion, Zelda's din's fire, Samus' charged shot/missiles/bombs, Doc's pills, Mario/Luigi's fireballs, ICs ice blocks, Yoshi's eggs, Link/YLink's boomerangs, Pika/Pichu's thunder jolts, M2's shadow balls, and G&W's sausages all staled in both damage and knockback in Melee. There may be a few more, but all other moves only staled in damage. If you noticed they're all projectiles, though not all projectiles staled this way for whatever reason (item based, living, and laser type projectiles don't).