Race/Class combinations you wouldn't play

[Tanarii]

Tiefling Barbarian.
But strangely, I've had a hankering to play a Halfling Barbarian Sailor (aka Viking) for a while now.

Dragonborn Sorcerer, even though they're as good as humans at it, ability score-wise.

Half-Orc Wizard, not even one that casts fist.

Mount Dwarf Druid, because wut? (If I did it would almost certainly be a Mountain Land Druid. Edit: or Underdark, on a seconds worth of reflection )

Also I still find it weird to play Dwarf or Halfling arcane caster, even after three editions of it being possible.