N-Gage Games
Brain Challenge
Brain Challenge provides a variety of different puzzle and logic games. The difficulty increases in conjunction with how well you do, and there are enough variations so that you never play the same puzzle twice.
DChoc Cafe Sudoku
This is sudoku of course, the game where you fill in the missing numbers. This version is part of the DChoc Café series, which tries to encourage community interaction as well as casual gameplay.
Reset Generation (formerly Project White Rock)
Reset Generation, previously codenamed Project White Rock, is a first party game published by Nokia and developed by RedLynx (who did Pathway To Glory and High Seize on the original gen N-Gage). Reset Gen is a turn-based strategy/puzzle game based around parodies of famous gaming characters, and will be available on both N-Gage and in a free web-based version too. There's an online multiplayer mode for up to four people, and an offline one-player story mode with cut scenes. The web-based version will be embeddable in your own website.
Snakes Subsonic
Snakes Subsonic is the sequel to Nokia's original N-Gage game Snakes, which was itself based a radical remake of the original 2D Snake game built into most Nokia phones.
Super Mah Jong
As far as we know, this is actually based on the puzzle game Shanghai rather than the board game Mah Jong.
Tetris
It's good old Tetris, the same block-spinning puzzle game that made so many people buy Game Boys.