I grew tomatoes years ago (just hybrids) and am pretty new to the heirloom / OP tomato growing. But I have found some favorites.
First of all, are you growing from seed, or buying plants from a local nursery? That'll greatly influence your choices - with seeds, the choices are unlimited. At the nurseries, you'd probably have to stick to more common plants.
Brandywine is a classic heirloom tomato. But there are a few different ones - hopefully you're getting the "real" one - a large pink tomato. There is also a Red Brandywine - also good, but not the same.
Another one to consider is the hybrid Brandy Boy - I grew this last year, and it was very good. A similary type to Brandywine, but produced more for me.
Cherokee Purple and Black Krim are both great tomato, I've grown them the past couple years, and are growing them again.
Beefsteak, Better Boy, Big Boy - all common tomatoes. They're fine, I've grown them in the past. But personally, I'd get something more interesting, if I could. Big Beef, for one, is a fairly common tomato, that I've heard a lot of good things about.
Early Girl never impressed me. I had a variety called New Girl that I liked better - not the best tasting, but it was early. Kind of firm, and worked pretty well for salsa. I see many comments about Bloody Butcher as a great early tomato also.
Super Sweet 100 is fine, but not my favorite. They are very sweet, but quite small.
Sungold and Black Cherry - can't beat 'em. They'll be on my list every year.
Yellow Pear - really really cute, but not a very good taste. I've reluctantly dropped this one.
If you're starting from seed, and want heirlooms/OP varieties, then I'm sure you can be quite overwhelmed with suggestions
