Way back in the day for PC it would have to be Cosmo's Great Adventure, and Doom.

I started modding games when the Quake 2 engine game out, and then got heavy into it when Quake 3 came out. Making a lot of mods for games such as but not limited to Medal of Honor Spearhead.

I then started on coding for Far Cry when it first came out, making a popular mod with my name in it, IcIrIs's Weapons Mod. Which allowed you to modify the weapon damages and a lot of other helpful things straight from the CFG file, VS extracting coding and re-compressing. It was also one of, if not the first, Server Side Mod for Far Cry.

Now I have gotten out of the Modding game, and just play them.