The term "obscure" is debatable, however I can think of plenty of underappreciated punk bands...
For those who like more catchy stuff...
Pinhead Gunpowder (A green Day side-project, think they're more stereotypivcal punk stuff like Insomniac or Kerplunk.), the Queers, Screeching Weasel, the Muffs..
For those who want old school...
Adverts, X-Ray Spex, Penetration, Vice Squad, Cock Sparrer (One of my favorites!) Avengers, X (Brilliant!), Germs (Great!)...
If you're looking for more underground/streetpunk stuff..
Check out The Trouble, Banner of Hope and Erika's second band New York Rel-X, Anti-Heroes, Intro5pect, Time Again, Oxymoron, Boston's own "The Unseen" mostly because I know them and they're cool, and Anti-Flag's "Die For You're Government" which is phenomenal.
I am an obsessive collector of punk and punk-related music, if you want more bands to check out, or specific tracks/albums I would be delighted to assist. I'd also recommend, as somebody already did, MunchyBrain, as a resource, especially for english street/anarcho-punk.