Como activar tercera persona.
Pegar el siguiente comando en tu autoexec

//Thirdperson (Campaing) - Tercera Persona (Campa�a)

bind "F8" "thirdpersonshoulder; togglezoom"; //# thirdpersonshoulder toggle bind (remove "togglezoom" to disable the mousewheel zoom feature)
alias "defaultzoom" "zoom.40"; //# default zoom distance for thirdpersonshoulder mousewheel zoom (change zoom.## to any multiple of 5 between 30 and 200)

// #############################
// thirdpersonshoulder fix & zooming
// #############################

c_thirdpersonshoulderoffset 0;
c_thirdpersonshoulderaimdist 720;
c_thirdpersonshoulderheight 10;
c_thirdpersonshoulderdist 40;
cam_ideallag 0;
cam_idealdelta 4;
cam_idealpitch 0;
cam_idealyaw 0;

alias togglezoom.off "alias up invprev; alias down invnext; alias togglezoom togglezoom.on; echo [l4d_ca: thirdpersonshoulder mode off ]";
alias togglezoom.on "alias up zoom.in; alias down zoom.out; up; down; alias togglezoom togglezoom.off; echo [l4d_ca: thirdpersonshoulder mode on ]";

alias zoom.25 "cam_idealdist 30; alias zoom.in zoom.30; alias zoom.out zoom.30";
alias zoom.30 "cam_idealdist 30; alias zoom.in zoom.25; alias zoom.out zoom.35";
alias zoom.35 "cam_idealdist 35; alias zoom.in zoom.30; alias zoom.out zoom.40";
alias zoom.40 "cam_idealdist 40; alias zoom.in zoom.35; alias zoom.out zoom.45";
alias zoom.45 "cam_idealdist 45; alias zoom.in zoom.40; alias zoom.out zoom.50";
alias zoom.50 "cam_idealdist 50; alias zoom.in zoom.45; alias zoom.out zoom.55";
alias zoom.55 "cam_idealdist 55; alias zoom.in zoom.50; alias zoom.out zoom.60";
alias zoom.60 "cam_idealdist 60; alias zoom.in zoom.55; alias zoom.out zoom.65";
alias zoom.65 "cam_idealdist 65; alias zoom.in zoom.60; alias zoom.out zoom.70";
alias zoom.70 "cam_idealdist 70; alias zoom.in zoom.65; alias zoom.out zoom.75";
alias zoom.75 "cam_idealdist 75; alias zoom.in zoom.70; alias zoom.out zoom.80";
alias zoom.80 "cam_idealdist 80; alias zoom.in zoom.75; alias zoom.out zoom.85";
alias zoom.85 "cam_idealdist 85; alias zoom.in zoom.80; alias zoom.out zoom.90";
alias zoom.90 "cam_idealdist 90; alias zoom.in zoom.85; alias zoom.out zoom.95";
alias zoom.95 "cam_idealdist 95; alias zoom.in zoom.90; alias zoom.out zoom.100";
alias zoom.100 "cam_idealdist 100; alias zoom.in zoom.95; alias zoom.out zoom.105";
alias zoom.105 "cam_idealdist 105; alias zoom.in zoom.100; alias zoom.out zoom.110";
alias zoom.110 "cam_idealdist 110; alias zoom.in zoom.105; alias zoom.out zoom.115";
alias zoom.115 "cam_idealdist 115; alias zoom.in zoom.110; alias zoom.out zoom.120";
alias zoom.120 "cam_idealdist 120; alias zoom.in zoom.115; alias zoom.out zoom.125";
alias zoom.125 "cam_idealdist 125; alias zoom.in zoom.120; alias zoom.out zoom.130";
alias zoom.130 "cam_idealdist 130; alias zoom.in zoom.125; alias zoom.out zoom.135";
alias zoom.135 "cam_idealdist 135; alias zoom.in zoom.130; alias zoom.out zoom.140";
alias zoom.140 "cam_idealdist 140; alias zoom.in zoom.135; alias zoom.out zoom.145";
alias zoom.145 "cam_idealdist 145; alias zoom.in zoom.140; alias zoom.out zoom.150";
alias zoom.150 "cam_idealdist 150; alias zoom.in zoom.145; alias zoom.out zoom.155";
alias zoom.155 "cam_idealdist 155; alias zoom.in zoom.150; alias zoom.out zoom.160";
alias zoom.160 "cam_idealdist 160; alias zoom.in zoom.155; alias zoom.out zoom.165";
alias zoom.165 "cam_idealdist 165; alias zoom.in zoom.160; alias zoom.out zoom.170";
alias zoom.170 "cam_idealdist 170; alias zoom.in zoom.165; alias zoom.out zoom.175";
alias zoom.175 "cam_idealdist 175; alias zoom.in zoom.170; alias zoom.out zoom.180";
alias zoom.180 "cam_idealdist 180; alias zoom.in zoom.175; alias zoom.out zoom.185";
alias zoom.185 "cam_idealdist 185; alias zoom.in zoom.180; alias zoom.out zoom.190";
alias zoom.190 "cam_idealdist 190; alias zoom.in zoom.185; alias zoom.out zoom.195";
alias zoom.195 "cam_idealdist 195; alias zoom.in zoom.190; alias zoom.out zoom.200";
alias zoom.200 "cam_idealdist 200; alias zoom.in zoom.195; alias zoom.out zoom.205";
alias zoom.205 "cam_idealdist 200; alias zoom.in zoom.200; alias zoom.out zoom.200";

togglezoom.off; c_thirdpersonshoulder 0;
defaultzoom;

//toggles through 3rd person,Resident Evil,Normal
bind f8 viewthird
alias viewthird "thirdpersonshoulder;cam_idealdist 100;cam_idealyaw 0;c_thirdpersonshoulderaimdist 140;c_thirdpersonshoulderheight 10;cam_ideallag 1; bind f8 regview"
alias regview "thirdpersonshoulder;c_thirdpersonshoulderaimdist 210;cam_idealdist 15;c_thirdpersonshoulderoffset 18;c_thirdpersonshoulderheight 5;cam_ideallag 1;cam_idealyaw 0; bind f8 normalv"
alias normalv "thirdpersonshoulder;c_thirdpersonshoulderoffset 0;c_thirdpersonshoulderaimdist 720;c_thirdpersonshoulderheight 10;c_thirdpersonshoulderdist 40;cam_ideallag 0;cam_idealdelta 4;cam_idealpitch 0;cam_idealyaw 0;bind f8 anotherv"
alias anotherv "thirdpersonshoulder;bind f8 viewthird"
m.200";

C_thirdpersonshoulderaimdist "720"
C_thirdpersonshoulderheight "5"
C_thirdpersonshoulderdist "90"
C_thirdpersonshoulderoffset "0"
cam_collision "1"
c_maxdistance "200"
c_maxpitch "90"
c_maxyaw "135"
c_mindistance "30"
c_minpitch "0"
c_minyaw "-135"