ChanServ
The IRC service that turned channels into something you could register and own, rather than something that belonged to whoever happened to still be there.
On early IRC a channel existed only as long as someone sat in it, and operator status went to whoever walked in first. That invited takeovers, especially after a netsplit. ChanServ fixed it by keeping ownership in a database outside the servers: the founder registers the channel, gets a tiered access list, and the service itself hands out ops to the right people as they join.
The model caught on at DALnet in the 1990s, together with NickServ. Undernet went its own way with a bot called X doing the same job. EFnet refused outright, and there channel wars survive as a kind of cultural heritage.