Plain. Allergic to peanuts... Dark chocolate ones good too.
I like them both, but I think that peanut M&M's are better.
Plain, I am not a big fan of nuts.
Funny that you asked this... I eat peanut M&M's every day in class....LOL... But you know... The ones I got yesterday were defective.... They were W&W's.....LOL
I like both of them, it just depends on the mood that I am in I guess. Lol
I like the plain ones, especially with the dark chocolate. I have to put some in a little dish and put the bag away usually, or I'll eat too many.