Our favorite grocery store tomatoes to use for sauce are Roma tomatoes, hands down.  They have very few seeds and their flesh is incredibly meaty and flavorful.  If you are a gardener and want to try to grow your own heirloom varieties, Amish Paste, San Marzano, Viva Italia, and Polish Linguisa tomatoes all make excellent fresh tomato marinara sauce, but are difficult to find fresh in the store: