Old mechanics that need to come back:
Echoing others:
--- 1e save categories (breath wpn., poison-paralyze-death, spell, etc.)
--- magic item destruction: on a failed save vs AoE damage ALL items carried must save
--- strongholds and followers at name level (along with the concept of name level!)
--- racial stat penalties as well as bonuses, with Humans - the baseline - getting neither
--- spell casting times and, thus, spell interruption
--- specific-to-weapon proficiencies, instead of just basic-martial-exotic
--- level drain
--- non-linear bonuses, similar to what 0e had (8-13 = +0, then a gentle J-curve each way from there)
Things I've not yet seen mentioned:
--- resurrection survival % roll (to make death more of a threat)
--- system shock % roll (this immediately curtails most abuses around polymorph other)
--- bend-bars/lift-gates % roll (far more granular than a d20 strength check)
--- cleric-vs.-undead matrix from 1e (and expand it a bit, there's lots of room there for more categories)
--- side-along multiclassing (as opposed to 3-4-5e additive) where each class advances independently
--- hard limits on multiclassing, both by number of classes allowed and by what can multi with what
--- roll-under-stat mechanics
--- take the caps off damage spells
Howzat?
