For the wee folk:
Gnomes, for me, will always be tricksters and pranksters, cunning, brilliant, deceptive, underhanded, giggling at others misfortune, constantly undermining authority, and giving a raspberry to the necromancer.
Halflings, for me, will always be Samwise. Not really Frodo. Not Merry. Absolutely not Pippin. Halflings are homespun and rural, they are doughty and resilient, they are wise and nurturing.
So, using 4e's tri-stat division:
Dwarves are Str/Con. They are a tiny warrior race. They are Fighters.
Gnomes are Int/Dex. They are a spry, agile, clever race. They are Rogues.
Halflnigs are Wis/Cha. They are practical and likable. They are Clerics.
Everyone who thinks halflings are sneaky, tricksy little ninjaes has, unwittingly, been fooled by a gnome who is pretending to be a halfling just to mess with the preconceptions of humans who think that a whole race of farmers and gardeners and borrow-builders is just too dull.