Well, I would recommend Project Nevada for New Vegas. It's sort of like a rebalancing overhaul that adds tons of new features and items to the game. Make sure you get the patches for the DLCs as well. Make sure to read the mod requirements too.
There's also Mission Mojave which fixes various bugs throughout New Vegas
Pip-Boy Readius, makes your Pip-Boy look more high tech and sexy (it's a matter of opinion). As for stuff that changes your HUD, I recommend these. (Install them in order according to this list), make sure to read install instructions.
1) MTUI makes the HUD more efficient by using empty space.
2) PipWare UI, makes your Pip-Boy interface look sexier and more compact.
3) The Mod Configuration Menu A menu that allows you to configure your mods, providing that the mods support MCM.
4) One Hud, Makes the HUD more immersive (Hides health bars and ammo if not in combat or not required), and enables your hunger/thirst/sleep on your hud, and allows you to adjust your HUD via MCM.
4.5)The Weapon Mod Menu, It overhauls the weapon mod menu, allowing you to remove weapon mods, and see which mods are available for the weapon even if you don't have it in your inventory.
5) Unified HUD Project, makes the other HUD mods compatible with each other.