Stalker Clear Sky, the second game in the original PC Stalker Trilogy, has a nice selection of mods, but I've picked out "Clear Sky Complete" because if you're looking for a mod with an item / weapon spawner, teleport fast travel, weather control and much more, it's very easy to install and works well.
Clear Sky Complete improves the graphics, sounds & gameplay on the base vanilla game & doesn't change the story, but please remember that this is an old mod for an old game, so make sure you've played through your first run of Clear Sky without any mods to avoid game-breaking bugs.
In this video I show you how to install the mod (very easy, just download the installer & run it on a clean Clear Sky installation), and how to configure it, by starting a game, going into the pause menu and pressing f1.
If you have problems with the Clear Sky Complete Mod crashing when the game is loading, uninstall & reinstall Clear Sky, reinstall the mod from the installer, and it should be ok.
So if you're to find the best mod for Stalker: Clear Sky with a cheat / trainer menu, Clear Sky Complete is a very good place to start.