What are your favorite custom sandwiches? For me it's always been simple ingredients, since I'm rather impatient when hungry. A few comments on some basic ingredients first.
Lettuce - Overrated really. I wouldn't say it adds to the sandwich in an way, and is mostly a tasteless filler.
Bread - Toasted can be way better. Take the extra time to put that bread in the toaster, your tastebuds will thank you.
Tomato - Tomatos rock in just about all sandwiches, but are rarely used by the common man.
Here's a few of my favorite recepies which are extremely simple, but tasty none the less. Bonus points for making up goofy names for your sandwiches.
Ted Koppel on a bike
Fresh sliced tomato
Mayo
Chicken breast
Toasted bread (naturally)
El tuna destructo
Tuna + mayo mixed (tuna salad)
Onions, lots of onions
Tomato
Toasted bread
I'm sure some of you have much more complicated Xtreme sandwiches so share away.