Basic Trope: Someone who shows (almost) no emotion, regardless of what happens.
Straight: Bob generally shows no emotions, whatsoever.
Exaggerated: Bob shows no emotion, ever. Even when his wife fell sick, when his daughter had her first birthday, at holidays, when his sister has an accident, when his little cat dies...
Downplayed: Bob does show emotion, but not to the same extent as his peers. When the situation calls to be happy, whereas other people would be cheering and have their arms in the air, Bob just has a slight smile. Or, when the situation calls to be angry, whereas other people would be shouting and making spit fly everywhere, Bob just gives a Death Glare.
Bob is an extremely powerful sorcerer who suppresses his emotion, because otherwise he will lose control of his powers.
Bob comes from a race where emotion is either suppressed or nonexistent.
Bob has found it... easier to not be emotional, either because he's that professional or because of an event in his past, but either way he has an easier time coping by being stoic.
Bob is a strict adherent of a philosophy that demands suppression of emotions.
Lampshaded: "You, know, Bob, normal people would be whooping and cheering right now."
Exploited: The Big Bad relies on transforming into the things that scare the heroes the most to defeat them. Bob's stoicism makes it so the Big Bad has no idea what he fears, allowing Bob to defeat him.
Defied: Bob's friends and family try their hardest to turn Bob into a Kuudere.
Discussed: "I wonder if Bob actually feels anything, or he really is that unemotional."
Conversed: "How does Bob hide his emotions so well?"
Bob's stoicism drives him into isolation, because the society he lives in values displays of emotion, or shuns those who refuse to show such.