I began using cinnamon raisin bread for mayo-based sandwiches way back when I was little... sounds like an odd combo huh? I thought so too. My Grama has always made mayo-based sandwiches on cinnamon raisin bread for as long as I can remember, and I used to be so weird-ed out by it, until I actually tried it myself. There's something about the combo that draws me in, I love the flavor, the sweetness and *shocker* I am addicted to it! My favorite combo is tuna on cinnamon raisin bred - my two loves smushed together!
Taking my two pieces of cinnamon raisin bread, I apply a thin layer of mayo on both pieces, then swirl on a generous amount of yellow mustard (my mustard amounts will always be "generous")
Layer a good amount of tuna mix on one piece of bread, I like to have it pretty thick, so I'm very heavy handed with my tuna portions
That's it! Sometimes I'll add lettuce or cheese, but as a quick snack, I just do this and it tastes surprisingly scrumptious!