I know I'm gonna take shit for this, but Skrewdriver actually used to be a fairly good Oi band before they became what most people know them as. I seriously doubt that many of their detractors have ever heard a single song of theirs.
All Skrewed Up was a pretty pure Oi album, and even later tracks like "This Little Piggy" and "Shove the Dove" are favorites of mine.
"If There's a Riot", "Boots & Braces", and "Mr. 9 to 5" are good offerings as well.
They really went to shit, in my opinion, when they got into the whole White Power thing and Ian Stuart switched from Cookie Monster to Dudley Do-Right.