We speedrun a lot of L4D and L4D2 (EXP, no glitches, no map skipping). Current records (see screenshots) are:
No Mercy - 13;
Crash Course - 7;
Death Toll - 15;
Dead Air - 12;
Blood Harvest - 12;
Sacrifice - 9;
NM HEM - 13;
DT HEM - 14;
DA HEM - 13;
BH HEM - 12;
Dead Center Veteran Mode (L4D) - 12;
Dead Center - 14;
Dark Carnival - 17;
Swamp Fever - 17;
Hard Rain - 15;
Blood Harvest L4D2 - 15;
Sacrifice L4D2: 11
Precinct 84: 17;
Suicide Blitz: 21;
City 17 - 17; and
Ravenholm - 20.