We grow sunflowers for our chickens. Some good black oil sunflower varieties are:
Perodovik (this is likely what you see bagged in stores)
For human seed snacking, we're more used to the striped varieties (although we can safely eat both). @Weedygarden, if you're growing in pots, I'd definitely keep an eye out for short varieties, since they are less susceptible to lodging:
Sunspot Dwarf - I've not grown these, but I think they're only 2ft tall!
Super Snack - these get to 5 feet
The downside of a shorter sunflower variety is that they will only have one flower head per plant. But those flower heads will be bigger (generally speaking) than those on a plant with multiple heads.