And, as always, if all of this text just makes your eyes hurt, enjoy the supplemental video synopsis here. It's fortified with 2,762% of our famous Joystiq Goodness™.
The premise of Onslaught is simple: shoot every space bug you see. Actually, there's a story that revolves around some planet, but who has time to pay attention to that when there are bugs that need killing? While the mission structures themselves vary, the means for accomplishing your goals usually come at the expense of many bug lives ... and many bullets. Thankfully the game avoids falling into a monotony-induced coma thanks to some very fun weapons and a variety of missions that keep things fresh.
At the outset, it seemed as though the arsenal of weapons at my disposal were nothing more than a generic lot, but the more I used them, the more I started to appreciate the varying pros and cons each weapon offered. Watching each gun tear into swarm after swarm of bugs, their blood splattering the ground and my facemask, was a pretty good feeling, and I found that each weapon had a situation that begged for its use (i.e. the shotgun is great on packs of flying bugs). Well, except for the rockets ... those things are always useful!
The mission structure was also a pleasant surprise. The more I advanced, the more I found myself wanting to advance. And for a $10 game on WiiWare, there's a lot to do in Onslaught, as each mission isn't simply just about going from Point A to Point B and shooting everything between. There are missions where I had to defend against an, uh, onslaught of attacking bugs, and other missions had me invading underground colonies to rid it of bug hives.
I wasn't alone throughout the game, either. My squadmates were constantly by my side, although their contributions weren't always apparent. I tried to get them into the fight more by changing formations, though I found this didn't really affect much. For the most part, the game depends on the player, and the squadmates might as well be on vacation, sipping margaritas.
There is also a pretty robust multiplayer experience available, with compatibility for co-op play through the single-player game's missions, but there's one problem: you can't find anyone to play with! At least, I couldn't, and I tried several times, only to be stuck watching a countdown timer slowly shave seconds away.
Hudson's FPS entry to WiiWare is an example of what great, cost-effective entertainment can thrive on the service. The missions have a great deal of polish, there are plenty of powerful guns to lay waste with, and it's an experience that rivals those found on retail discs, but for 1/5th of the price.