A French dip is a sandwich composed of bread and at least one other component--typically close-faced--that is dipped into a hot broth or gravy. It doesn't have to be beef and there are examples of vegetarian French dips. The classic French dip is a French baguette with roast beef dipped into pan drippings. The dipping can occur either by the eater or before serving (served "wet").
See the Wikipedia page about French dips.
Giuseppe (what is this? Grim's in Seattle has it with their dip...)
Meats (or the main protein-like substance)
Roast beef (can be served rare for style and taste/flavor like at Grim's Seattle)
Ham (Turf, Seattle)
Lamb (recipe here)
Portobello Mushroom(s) (like from Cafe Flora, Seattle)
Non-Meat Toppings (Accompaniments)
Smoked Onions (Redmond's Bar & Grill, Redmond, WA)
French Fries (Tat's Deli, Seattle)
Ancho Chile Au Jus (Peso's Seattle)