Basically, any sandwich that does not contain pig products such as ham and bacon has the potential to be one of thousands of halal sandwiches on offer around the world. Other meats, such as chicken and beef, are OK so long as the animals have been slaughtered in a traditional Muslim manner. All seafood is considered halal by the majority of Muslims. Food cannot be prepared or contaminated by these products or by alcohol, blood, carrion or birds of prey. Halal sandwiches include the ploughmans, the corned beef Reuben, the Louisiana Po' boy and the cheesesteak.
All breads are good for halal sandwiches. This means a variety of bread types can be employed including white and wholemeal/whole-grain bread. These are OK so long as no pork products such as pig fat oil are used to bake the bread. If the sandwich is buttered, then it must be done so without pig lard or butter, with margarine made from vegetable oil being a satisfactory alternative.
In terms of meat, all chicken, turkey, beef and seafood sandwiches are halal. These range from Caesar chicken to smoked salmon and cream cheese. This means sandwiches such as the cheesesteak are allowed, but the club sandwich would have to have the bacon removed. The BLT would not be halal.
It is possible to make some sandwich recipes that ordinarily have bacon, ham or other pork products in them. While in many cases the ham or bacon could just be removed, it is also possible to replace those products with chicken or turkey ham. The taste would be a little different, but it is as close to the original taste as halal sandwiches can get without breaking the rules.
All vegetable sandwiches are halal sandwiches. This includes sandwiches such as the bulgur burger, the cucumber sandwich and the grilled cheese. Toasted panini and Italian-style sandwiches with tomato or bologna sauce, mozzarella or pesto sauce are all halal sandwiches. The ploughmans, a favorite of English pub lunches, is also a halal sandwich, as are peanut butter and jelly sandwiches.
To get halal status for certain sandwiches would depend on how they are prepared. These include the chip butty, which is traditionally made with fat English chips, known as fries in America, and the crisp sandwich, which is made with potato chips. Both of these products would be halal if the potato is fried in vegetable oil rather than the traditional pig fat oil.