Here's my first entry this year, B4k. It's a Berzerk clone which looks a bit similar to Gridblaster4k, the entry I coded up last year.
The .jar weighs in at 4,088 bytes. It uses procedural graphics (it's obviously all done with polygons) and a particle engine to handle explosion effects.
Your goal is simply to destroy as many robots as you can while avoiding both the robots and the invincible Evil Otto. The arrows control your movement, space fires, and escape quits.
The only issue I really have with the game right now is that I can't find a way to either make the close box work or grey it out that doesn't push the game over the size limit.
The self-executing .jar file is at http://www.w4jdh.net/~seigfried/j4k/b4kv6.jar
; it should run on a computer with Java 1.3 or later. Let me know what you think!