Silverlight TruckWars is a real-time strategy game built entirely in Silverlight. I recently releases version 1.3. The biggest thing is that I've now open-sourced it on CodePlex.
I've also added several enhancements
Added hold-able objects, like a key
The biggest one is that selecting any creature now provides help text.
Destroying an enemy unit now can optionally provide a "treasure", like a powerup or key.
Lots more powerups:
Bounce - projectile bounces off walls
Thrust - doubles your thrust
Clone - clones the creature that got the powerup
Health - plus 50 health points
New creatures & levels