Input the following values into the "changelevel [map name]" or "map [map name]" code to play on that map:

Campaign mode
LEVEL - CHEAT CODE
No Mercy: The Apartments - changelevel l4d_hospital01_apartment
No Mercy: The Subway - changelevel l4d_hospital02_subway
No Mercy: The Sewer - changelevel l4d_hospital03_sewers
No Mercy: The Hospital - changelevel l4d_hospital04_interior
No Mercy: Rooftop Finale - changelevel l4d_hospital05_rooftop
Death Toll: The Turnpike - changelevel l4d_smalltown01_caves
Death Toll: The Drains - changelevel l4d_smalltown02_drainage
Death Toll: The Church - changelevel l4d_smalltown03_ranchhouse
Death Toll: The Town - changelevel l4d_smalltown04_mainstreet
Death Toll: Boathouse Finale - changelevel l4d_smalltown05_houseboat
Dead Air: The Greenhouse - changelevel l4d_airport01_greenhouse
Dead Air: The Crane - changelevel l4d_airport02_offices
Dead Air: The Construction Site - changelevel l4d_airport03_garage
Dead Air: The Terminal - changelevel l4d_airport04_terminal
Dead Air: Runway Finale - changelevel l4d_airport05_runway
Blood Harvest: The Woods - changelevel l4d_farm01_hilltop
Blood Harvest: The Tunnel - changelevel l4d_farm02_traintunnel
Blood Harvest: The Bridge - changelevel l4d_farm03_bridge
Blood Harvest: The Train Station - changelevel l4d_farm04_barn
Blood Harvest: Farmhouse Finale - changelevel l4d_farm05_cornfield

Versus mode
LEVEL - CHEAT CODE
No Mercy: The Apartments - changelevel l4d_vs_hospital01_apartment
No Mercy: The Subway - changelevel l4d_vs_hospital02_subway
No Mercy: The Sewer - changelevel l4d_vs_hospital03_sewers
No Mercy: The Hospital - changelevel l4d_vs_hospital04_interior
No Mercy: Rooftop Finale - changelevel l4d_vs_hospital05_rooftop
Blood Harvest: The Woods - changelevel l4d_vs_farm01_hilltop
Blood Harvest: The Tunnel - changelevel l4d_vs_farm02_traintunnel
Blood Harvest: The Bridge - changelevel l4d_vs_farm03_bridge
Blood Harvest: The Train Station - changelevel l4d_vs_farm04_barn
Blood Harvest: Farmhouse Finale - changelevel l4d_vs_farm05_cornfield