THAC0
Shorter to run combats
The flavor of settings from 2E
The more "epic" feel of earliest editions where leveling up was a big thing rather than a calculated progression.
Magic items with style even if they were generally worthless or just weird. (Mist Tent, etc.)
Ral Partha minis
True, I do miss the shorter combats - or large scale gigantic combats that were easier to run in 2E days. I remember, we had 10 PCs (big group), 2 major NPCs and about 20 caravan guard types on our side, vs 80 lizardmen, a lizard shamen or two, giant dragonflies, a giant croc and snake, plus a summoned elmental from the shamen. All in one great session.
If I wanted to do that with 3E, it would take 5 sessions or more.