Definitely helps the world feel more alive when you're actually got stuff in the distance to look at. 'FNVLodGen' is a small one but it really helps - it helps stop the pathetically small render distance of objects like rocks and plants. 'Craftpack' adds a ton (1000+) of crafting recipes if you like playing that sort of character, and 'Ammo Ingredients Loot' is a small one which helps to get more use out of the ammo crafting system. 'Mission Mojave' contains a ton of fixes for bugs, both small (floating rocks) and large (broken quests). 'NMC's Texture Pack' improves overall texture quality quite a lot, and 'Essential Visual Enhancements' also does quite a lot to help the game look more modern. 'Wasteland Flora Overhaul' helps made the game feel a bit more alive by adding some more vegetation. 'Realistic Weapon Damage' helps make the combat a little more fast-paced, and 'More Realistic Aiming' lets you control how accurate your character gets from levelling up the various weapon skills (by default, some weapons are just unusable) - as a bonus, the extra accuracy is also reflected by the dynamic cross-hair from Project Nevada! 'Weapon Mods Expanded' adds a ton of new weapon modifications and helps clean up compatibility issues with unique items, so you can get a bit more creative with them. Definitely helps the world feel a little less empty, especially in areas which are otherwise woefully underused.

'A World of Pain' adds a ton of new areas to explore, complete with loot and enemy encounters. 'Project Nevada' as others have said - adds a dynamic cross-hair, grenade & sprint hotkeys, bullet-time as a VATS alternative and helps smooth out the gunplay a lot.

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