Here are some screenshots from various (articial) combination situations, taken from one of my programs. Notice I'm not as focused on the look of my program as I suppose I could be. Scroll over the links for small versions of the pictures, click for a larger version. If you want to see these combos in action, try my applet.

Squares: 4x4, 5x5, 5x5, 6x6.

Viruses: 57 64 67 68 72

Sadly, I can only take credit for the 4x4 and 57 virus combos. The others were from discussion on a gamespot forum that seems to have since disappeared.

Additionally, my friend Keith animated the 57 virus combo, creating this spiffy gif.