I'm looking for a place to get good EVs for Tentacruel, Jynx and Venusaur for the Elite Four so I'm looking for a good place to train them without giving them useless EVs.
Gastly gives 1 Special Attack EV and Haunter gives 2, Cubone is so rare they won't be disturbing you much.
If you want to train Special sweepers, then Route 1 and Altering cave are some good spots for Speed EVs.
You really don't need EV trained Pokémon for in-game use though.
FRLG EV training hotspots