Do some angus cattle have horns?

It's possible, however all registeterd Angus cattle are polled. A few animals may be scurred, but that's not that common. Any black cattle that are horned are not fullblood or purebred Angus. The various Angus Associations around the world will not recognize horned black cattle as Angus cattle when a producer tries to register such animals.

The scurs or horns (if they do present themselves) come from the influence and breeding-up done by producers when they have introduced Jersey and Shorthorn (earlier in the breed's history) into the Angus bloodline to deter from too much inbreeding. Both of these breeds are horned, Jersey moreso today than Shorthorn, and it should be no surprise that horns or scurs may come up in some fullblood or "purebred" Angus cattle. But as mentioned above, if such animals come about, they do not qualify to be registered and are only recognized as commercial Angus cattle.