This is a rather basic mod that replaces the buggy with the "Spotter" from the Mad Max game. I've also taken the liberty to modify the Gauss Rifle to it better resembles its viewmodel a bit. It contains a script that makes the car go ...
It's generic Half-Life 2 Pistol but player holds it with both hands. Replaces the stock one. Only model is replaced, so it's compatible with retextures. Extract folder inside archive to Half-Life 2/hl2/custom/
<font color="#009900"><i>Left 4 Dead 2 survivors replace Half-Life 2 characters. All models survivors taken from Left 4 Dead 2. Now for Half-Life 2 and Episodes</i></font>