Credits: Unknown, taken from R15's Omega Hook source, menu code from Harlequin by Stealth-X, tutorial written by me.

-client.cpp

Somewhere under your includes add:
CODE

void DrawAimVecMaker();

Somewhere add:
CODE

void gDrawFilledBoxAtLocation2( float* origin, int r, int g, int b, int a, int radius=1)
{
    float vecScreen[2];
    if( !CalcScreen(origin, vecScreen) ) { return; }
    int radius2 = radius<<1;
    gEngfuncs.pfnFillRGBA(vecScreen[0]-radius,vecScreen[1]-radius,radius2,radius2,r,g,b,a);
}
cl_entity_s vecDummy;
void DrawAimVecMaker()
{
    vec3_t aim_location, target_origin;
    vec3_t up, right, forward, playerAngles;

    vector<aimvec>::iterator pos, end;
   if(vecDummy.curstate.usehull == 1)
    {
        pos = gAimbot.AimVecsS.begin();
        end = gAimbot.AimVecsS.end();
    }
    else if(vecDummy.curstate.usehull == 2)
    {
        pos = gAimbot.AimVecsD.begin();
        end = gAimbot.AimVecsD.end();
    }
    else if(vecDummy.curstate.usehull == 6)
    {
        pos = gAimbot.AimVecsJ.begin();
        end = gAimbot.AimVecsJ.end();
    }
    else
    {
        pos = gAimbot.AimVecsS.begin();
        end = gAimbot.AimVecsS.end();
    }

    // calculate aiming vectors
    playerAngles[0]=0;
    playerAngles[1]=vecDummy.angles[1];
    playerAngles[2]=0;
    gEngfuncs.pfnAngleVectors (playerAngles, forward, right, up);
    forward[2] = -forward[2];

    register DWORD color = 0xFFFFFF;
    float vecScreen[2];
    int num = 0;
    for (;pos!=end;++pos)
    {
        aim_location[0] = vecDummy.origin[0];
        aim_location[1] = vecDummy.origin[1];
        aim_location[2] = vecDummy.origin[2];

        aim_location = aim_location + forward * pos[0].f;
        aim_location = aim_location + up * pos[0].h;
        aim_location = aim_location + right * pos[0].r;
       
        gDrawFilledBoxAtLocation2(aim_location,192,255,255,255,1);
        float r = ((color&0xFFFFFFFF)>>24)/255.0;
        float g = ((color&0xFFFFFFFF)>>16)/255.0;
        float b = ((color&0xFFFFFFFF)>>8 )/255.0;
        gEngfuncs.pfnDrawSetTextColor(r,g,b);

        if( CalcScreen(aim_location,vecScreen) )
        {
   
            char buf[3];
            sprintf(buf,"Sequence: %d",vecDummy.curstate.usehull);
            gEngfuncs.pfnDrawConsoleString(vecScreen[0],vecScreen[1]+3,buf );
        }
        color = 0xFFFFFFFF;
    }
}
void func_vecdummysnap()
{
    cvar.vecmaker_x = me.pmEyePos[0]-80;
    cvar.vecmaker_y = me.pmEyePos[1];
    cvar.vecmaker_z = me.pmEyePos[2];
}
In hud_redraw add:
CODE     if (cvar.vecmaker) 
    {
        DrawAimVecMaker ();
    }

In hud_addentity, under if(bNewFrame), delete bNewFrame = false; and add:
CODE

    {
        bNewFrame = false;
        if(cvar.vecmaker)
        {
            memcpy( &vecDummy,me.ent, sizeof(cl_entity_s) );

            vecDummy.curstate.sequence = me.ent->curstate.sequence;
            vecDummy.curstate.usehull = me.ent->curstate.gaitsequence;
   
            switch(cvar.dummytype)
    {
        case 0:

            vecDummy.origin[0] = cvar.vecmaker_x;
            vecDummy.origin[1] = cvar.vecmaker_y;
            vecDummy.origin[2] = cvar.vecmaker_z;break;   

    case 1:   
            vecDummy.origin[0] = me.ent->origin[0];
            vecDummy.origin[1] = cvar.vecmaker_y;
            vecDummy.origin[2] = cvar.vecmaker_z;break;
       
    case 2:
            vecDummy.origin[0] = cvar.vecmaker_x;
            vecDummy.origin[1] = me.ent->origin[1];
            vecDummy.origin[2] = cvar.vecmaker_z;break;
                }

            VectorCopy( vecDummy.origin, vecDummy.curstate.origin );
       
            vecDummy.angles[0] = cvar.vecmaker_pitch;
            vecDummy.angles[1] = cvar.vecmaker_yaw;
      //    vecDummy.angles[0] = me.ent->angles[0];
      //    vecDummy.angles[1] = me.ent->angles[1]-180;

            vecDummy.curstate.frame = cvar.vecmaker_frame;

            gEngfuncs.CL_CreateVisibleEntity(ET_NORMAL,&vecDummy);
        }
    }

cvar.cpp, cvar.h

Register your cvars:
CODE

    REGISTER_CVAR_FLOAT( vecmaker_z, 0.00)
    REGISTER_CVAR_FLOAT( vecmaker_y, 0.00)
    REGISTER_CVAR_FLOAT( vecmaker_pitch, 0.00)
    REGISTER_CVAR_FLOAT( vecmaker_yaw, 0.00)
    REGISTER_CVAR_FLOAT( vecmaker_x, 0.00)
    REGISTER_CVAR_INT( vecmaker, 0)
    REGISTER_CVAR_INT( vecmaker_frame, 0)
    REGISTER_CVAR_INT( dummytype, 0)

    float vecmaker_pitch;
    float vecmaker_yaw;
    float vecmaker_x;
    float vecmaker_y;
    float vecmaker_z;
    int dummytype;
    int vecmaker;
    int vecmaker_frame;

OGC Menu Code:
CODE

" " "[Built-In Modeler]"{ //Built in model for you to make vecs
" " "-Modeler on/off" "vecmaker change;vecdummysnap"//Toggle modeler on and off
" " "-Snap Modeler To You" "vecdummysnap"//Brings the model toward you
" " "-Dummytype Strafe " "vecdummysnap;dummytype 2"//Allows you to tweak rights
" " "-Dummytype Normal" "vecdummysnap;dummytype 0"//Keep the model still
" " "-Dummytype Down/Up " "vecdummysnap;dummytype 1"//Allows you to tweak forwards
}