
This was a combination cell phone/handheld game console released by Nokia in 2003. It was known for its rather...unique design quirks. For instance, you needed to change games by taking off the back plate of the N-Gage, taking out the battery, and then change out the card. There's also the way you talked on the console, which looked like this:

(art by ParseNoire)
This was a phenomenon known as "sidetalking", which inspired a series of early memes. The original sidetalking website is still alive and kicking for your perusal.
A lot of the design quirks of the N-Gage would be fixed with the N-Gage QD, which allowed you to talk on it like a relatively-normal-looking N-Gage owner and had an external cartridge slot. Also the buttons felt more like game console buttons and less like phone buttons.

In total there were 65 games released on this console during its two year lifespan. Some notable examples include Advance Wars clone High Seize, a series of GBA & PSX ports (including Tomb Raider, Sonic Advance being ported as Sonic N, etc.), and the only known video game adaptation of the Rifts tabletop game.
I've been obsessed with this perfect piece of mediocrity for years (and currently own 6 of them); anyone else have "fond" memories of this thing?