Ghost Squad is a return to old-school lightgun games of the late 90s/early 00s that feels right at home on the Wii.

Why is it so nice on the Wii? Well, because the Wiimote acts as your gun. Old-style light guns only worked on CRT screens, so people with DLP/projection, plasma, and LCD TVs were sunk. However, since the Wiimote uses an optical sensor (with the Wii sensor bar), it works on any television.
Another advantage is that the Wiimote is the main piece of hardware, so you don't need to buy an entire light gun if you want it to perform like one - you just need an appropriate husk. This makes it much more cost effective.
Your first choice should probably be the Wii Zapper because it comes with the very fun Link's Crossbow Training.
http://www.nintendo.com/wii/what/accessories/zapper
However, Tina and I have found the Perfect Shot to be far and away the best feeling gun for straight light gun games:
http://www.nyko.com/nyko/products/?i=124
This gun has just the right look and feel. The trigger feels great and has good resistance/recovery (spring loaded).
OK, back on track...
Ghost Squad allows you to calibrate the guns to the screen. I noticed that the vertical boundaries are a little restrictive and that I have to aim a little higher than what is natural for it to detect properly (sensor bar is on top). I haven't tried it with the sensor bar on the bottom to see if there is a difference. In any case, it doesn't really affect gameplay once you've shot a few enemies and have calibrated your brain to it.
You and your friend(s) play the roles of members of a tactical combat team. It is your job to save hostages and take out terrorist threats.
The game runs on rails in a first-person perspective. If you've ever played House of the Dead or any other standard light gun game, you know what to expect. Reloading is done simply by pointing off the screen. There are branching paths that add some variety to your adventure.
In addition to the standard "shoot the enemy and avoid killing hostages" you sometimes need to accomplish special tasks. You will need to use the A button to interact with certain objects (like disarming bombs and also melee cutscenes). The boss fights also have certain objectives that differ from the standard shoot and kill. For example, the first boss fight provides you with a rocket launcher. You must keep your target over the moving chopper for a few seconds to lock on before you can fire.
My favorite scenes are probably the sniping ones. The feel is incredible. You get one shot before each reload, so you really want that bullet to count. And there's just some sick satisfaction from picking off sentries before they even see you. Often they are in pairs, so seeing them react to it is pretty entertaining.
One thing I thought was a little weak was the enemy deaths. When you shoot them, you just don't get that "oomph" nor is there much gore to accompany it. If anything, it probably leans more to the realistic side of things, but I'd much rather see enemies fly back or have parts explode on impact. I guess I am just spoiled by the great damage animations in House of the Dead.
Although the game tries to evoke a sense of seriousness to dire situations (it's cool when the squad leader is assigning flanking tactics and so forth), the overall feel comes off as campy. This is a plus in my opinion. As an example (and this is a spoiler, but honestly it doesn't really matter in a game like this): At the end of mission 2 there is a guy holding the president of the Unites States hostage on AirForce1. You basically shoot that guy in the head and jettison him out of the cargo hold. The president then proceeds to thank you and then
high fives you. I'm serious. This is like "Bad Dudes" quality awesomeness.
There are only three missions and each will only take about 7 minutes to complete. So you're talking game completion in 20 minutes - there are also unlimited continues. However, there is an experience and level system, so as you progress you unlock more difficult versions of the same levels. This in turn also unlocks different types of weapons, costumes, more branching paths, and other surprises. There are tons of things to unlock.
I would much rather have a short, but super fun game than a long and boring one. This game delivers and it is the perfect game to bust out for a quick shooting session to take out terrorist scum. It's just fun to play. Period.
There is a training mode with mini games that can be played competitively with friends. There is also a "party mode" which is pretty much the same as the regular arcade mode (which is up to 2 players), except you can actually play up to 4 player coop at the same time.
I give the game an 8.0 on the sinlgle player scale and a nice
8.5 on the coop scale. This game is very coop friendly and is great fun to pick up and play at any time. It's biggest drawbacks are lack of variety/shortness and weak kill animations. This game retails for $30 and I would say that's not a bad price, but you might want to hold out for a used/discounted price. At $20 I would say this is far and away a fantastic purchase.