Plants vs. Zombies
Final boss battle: awesome.
By the credits-slash-hilarious-music-video, I had been challenged, but not put out. Even in the later levels, I was usually able to win on my first attempt, though sometimes by the skin of my teeth. But after beating the final level, a slew of new stuff unlocks to push you even further.
This stuff includes replaying the full "adventure" mode with some handicaps; survival challenges from each of the game's settings; and more puzzles and mini-games, most of which I tried and some of which are really hard. Some of the final puzzles actually do become puzzle-like, in requiring you to figure out an exact sequence of actions to complete the stage. And the mini-games are always a riot, many of them parodying PopCap titles (like "Beghouled" and "Zombiquarium") or other games ("Portal Combat"). It's really impressive how the game manages to wrap itself around so many disparate gameplay concepts, and trying a new one is always a blast. Except "Beghouled Twist" - that sucked.
And there's a "Zen Garden" mode, where you can actually grow plants, to earn money. Or just for fun. It's a little esoteric.
On top of being a damn fun game, Plants vs. Zombies is absolutely loaded with content, content that I'd love to revisit at some point. This game is a victory for anyone who wishes they'd make 'em like they used to. Being funny doesn't hurt, either.
Progress: Silver trophy