Link's Crossbow Training
The Wii Zapper controller shell retails for $20 and comes with this game. So your expectations might be pretty damn low. But Link's Crossbow Training is surprisingly cool.
There are three different kinds of levels, basic target shooting, "Defender" (take out approaching targets), and "Ranger" where you have to move around and aim at the same time. Controlling the Ranger mode was really disorienting at first, but after a couple levels it's easy to get the hang of.
The gameplay isn't all that complex: shoot shit. As in Phantom Hourglass's shooting gallery, you beef up a point multiplier with consecutive hits, so in general you really want to not miss. Getting more points gets you better metals (Bronze, Silver, Gold, Platinum), which probably doesn't mean anything, but is still fun in a score-attack kind of way.
There are nine levels, each of which has three stages, so there is actually quite a bit of variety. There are even - spoilers? - two boss battles in the last levels. The multiplayer isn't as cool as you may think, as it's just taking turns and trading off the zapper, but as a single-player venture I think Crossbow Training rivals any House of the Dead or Time Crisis. And for the price, it's hard to go wrong.
Progress: Need more medals!