Fallout: New Vegas has seen a torrent of mods, many of them simply adapted from their Fallout 3 counterparts, and PC Gamer offers a top 25 of mods so far, a varied offering with many different type of mods.
1. Centred third person camera
Why did Bethesda give us the weird over-the-shoulder cam in Fallout 3? Why didn't Obsidian get rid of it for New Vegas? We may never know. Probably because they imagined players actually trying to take aim and fire in third person mode, which is insane. Third person is for screenshots and lightsaber fights we've known that since Jedi Knight 2! Fortunately, every time a developer does this, one of the lovely modder people undoes it.
This mod also lets you zoom all the way out. How far? All of the far, that's how far.
2. Black Company improved perks
A whole slew of balanced, interesting perks. It comes in two flavours both are available at any level, but require you to meet certain criteria. In the first version, you need to have high abilities those are the things you pick at the start and can only occasionally increase. The second version is identical, but requires you to meet skill point thresholds instead. They're all wonderfully inventive and cover a wide range of interests and specialist player archetypes left out in the cold by Obsidian's vanilla perks.