The problem with a lot of packs, imo, is low quality textures (i.e. too symmetric, misaligned) or overpowered weapons that make an easy game even easier. That being said, I enjoy these:
- http://www.newvegasnexus.com/downloads/file.php?id=39754
- http://www.newvegasnexus.com/downloads/file.php?id=37553
- http://www.newvegasnexus.com/downloads/file.php?id=39651
Nordic Firearms is especially impressive for its variety and quality, but I don't hear much talk about it on the forums so I think it's relatively obscure.