I've always been a fan of Hardcore.
It's my personal opinion that Diablo II Hardcore BattleNet was a pinnacle of gaming history. The PvE and PvP there was such high stakes.
Anyone else remember the people who made Charge Pallys for the sole purpose of logging into a game and murdering all the players?
This server has also been a time-sink for me. One-Month Deathban full PvP:
Hardcore Survival Multiplayer