Good recommendation was made to pick up a couple Perfect Shots for the wii remote(think they were $14.99 at Amazon last I saw) so you don't have to fire the remote like a star trek phaser.
All the good on-rails shooter games were recommended.
I'm a PC gamer used to a mouse and keyboard for my FPS action so I have difficulty moving with the nunchuck while aiming/shooting with the remote. Therefore after trying Metroid Prime I switched over to the on-rails shooters once they started becoming available.
I've played Ghost Squad which I found short with only 3 campaigns but due to unlockables and multiple routes it increases the replayability.
House of the Dead 2 & 3 I've played a little of so far and it retains all of its arcade cheesiness but it was kind of annoying to have to play and fail several times just to increase my health and lives for subsequent play-throughs.
Links Crossbow Training I picked up in trade since I didn't want the zapper. While its fun, worth the cheap price you can get it for used and offers control variety through the different minigames, the multiplayer is essentially single player as I'm sure they designed the game for players that would be sharing the bundled zapper.
Hopefully my wife will pick up Resident Evil: Umbrella Chronicles for me for Christmas.
Lastly, one game that hasn't been mentioned yet is Raving Rabbids. I have the first game in the series and the on-rails shooter levels(think there are about 10) are a blast. You get to shoot bunnies with plungers, a couple power ups, blow a few environmental items up, shoot the musical item on the level to get them all to stop and dance, and finally take on the boss at the end. There's beach, western, graveyard, sci-fi, etc. settings and each is pretty damn fun. If playing solo, the nunchuck can be used to grab/hold/throw the rabbids, where in multiplayer I think you just both get to shoot.
While it is a lot of fun, the downside is that you need to play though the single player mode to unlock the shooter levels to be played separately(the shooter games are the finales to each tier in single player mode). While most of the minigames are funny and enjoyable it would have been nice to be able to play all of the minigames on demand up front. Also I found this game to require you to be closer to the screen then some of my other games but maybe the range is just an issue because I have to keep my sensor on top of the TV out of my daughter's reach.