Top 10 Lettuce Varieties

Its full name is Boston Butterhead Lettuce but at least in Canadian stores it goes by Boston Lettuce for short.
It's very tender, crispy and juicy.

(a.k.a. French Crisp or Summer Crisp)
It stays crisp, doesn't bolt and doesn't turn bitter as easily as other lettuces. It can hold better in the heat than other varieties.
Batavia Lettuce leaves can be all green or burgundy red-tinted. There isn't a taste difference between the two, so choose the color you like (or use both).

Aka Continuity.
The leaves stay tender even when they're bigger than a human hand. It's a very beautiful butterhead lettuce variety - it has green leaves tinged with red or bronze. It can be grown all year round in mild-winter gardens.

There are 2 varieties: Red Oak Leaf' and 'Green Oak Leaf.
Oak Leaf Lettuce stays tender longer and take longer to become bitter. Slower to bolt.

I swear I didn't make it up! (I mean, the name of this lettuce)
I will add images to prove it does exist (and it tastes good).

It's relatively tender. This is probably the most common lettuce type in Canadian grocery stores along with Iceberg and Romaine (Boston, Batavia and Rucola are also available but are a bit more expensive)

Probably its biggest advantage is that when unwashed it can keep for up to two weeks in the fridge (it's longer than the other types).
It's juicy, crispy and hardy. But it isn't as flavorful as other lettuces.
Firm, densely packed heads that are heavy for their size are better.
Best dressing: cheese-based (Three Ranch Cheese, Blue Cheese)

It has slightly bitter leaves and some people don't like this bitterness but several drops of honey or maple syrup will help to neutralize this bitterness.
Center ribs are sweeter and they are known as Romaine Hearts (available in stores).

It is a variety of the Buttercrunch Lettuces - they are crosses between butterhead (bibb) and romaine varieties. Winter Density has thick, dark-green leaves in a vertical rosette.