In D&D 4th ed, Gnomes aren't even included as a core race. In 3/3.5, they were a clannish, xenophobic, semi-subterranean people who specialized in gems and illusions, and exhibited a faerie-like tendency for tricks and mischief.

I think most people's views of gnomes these days is colored by MMOs, which was in turn colored by Dragonlance. Both Everquest gnomes and Warcraft gnomes are tinkerers, and live[ed] in towns characterized by mechanical, steam/coal/clockwork-powered wonders, and exhibit a tendency to be blown up, much like the Tinkergnomes of Dragonlance.