Task: Forest fire
C#: using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Threading;
using System.Windows.Forms;

namespace ForestFire
{
    class Program : Form
    {
        private static readonly Random rand = new Random();
        private Bitmap img;

        public Program(int w, int h, int f, int p)
        {
            Size = new Size(w, h);
            StartPosition = FormStartPosition.CenterScreen;

            Thread t = new Thread(() => fire(f, p));
            t.Start();

            FormClosing += (object sender, FormClosingEventArgs e) => { t.Abort(); t = null; };
        }

        private void fire(int f, int p)
        {
            int clientWidth = ClientRectangle.Width;
            int clientHeight = ClientRectangle.Height;
            int cellSize = 10;

            img = new Bitmap(clientWidth, clientHeight);
            Graphics g = Graphics.FromImage(img);

            CellState[,] state = InitializeForestFire(clientWidth, clientHeight);

            uint generation = 0;

            do
            {
                g.FillRectangle(Brushes.White, 0, 0, img.Width, img.Height);
                state = StepForestFire(state, f, p);

                for (int y = 0; y < clientHeight - cellSize; y += cellSize)
                {
                    for (int x = 0; x < clientWidth - cellSize; x += cellSize)
                    {
                        switch (state[y, x])
                        {
                            case CellState.Empty:
                                break;
                            case CellState.Tree:
                                g.FillRectangle(Brushes.DarkGreen, x, y, cellSize, cellSize);
                                break;
                            case CellState.Burning:
                                g.FillRectangle(Brushes.DarkRed, x, y, cellSize, cellSize);
                                break;
                        }
                    }
                }

                Thread.Sleep(500);

                Invoke((MethodInvoker)Refresh);

            } while (generation < uint.MaxValue);

            g.Dispose();
        }

        private CellState[,] InitializeForestFire(int width, int height)
        {
            
            var state = new CellState[height, width];
            state.Initialize();
            return state;
        }

        private enum CellState : byte
        {
            Empty = 0,
            Tree = 1,
            Burning = 2
        }

        private CellState[,] StepForestFire(CellState[,] state, int f, int p)
        {
            
            var newState = (CellState[,])state.Clone();

            int numRows = state.GetLength(0);
            int numCols = state.GetLength(1);

            for (int r = 1; r < numRows - 1; r++)
            {
                for (int c = 1; c < numCols - 1; c++)
                {
                    
                    switch (state[r, c])
                    {
                        case CellState.Empty:
                            if (rand.Next(0, p) == 0)
                                newState[r, c] = CellState.Tree;
                            break;

                        case CellState.Tree:
                            if (NeighborHasState(state, r, c, CellState.Burning) || rand.Next(0, f) == 0)
                                newState[r, c] = CellState.Burning;
                            break;

                        case CellState.Burning:
                            newState[r, c] = CellState.Empty;
                            break;
                    }
                }
            }

            return newState;
        }

        private bool NeighborHasState(CellState[,] state, int x, int y, CellState value)
        {
            
            for (int r = -1; r <= 1; r++)
            {
                for (int c = -1; c <= 1; c++)
                {
                    if (r == 0 && c == 0)
                        continue;

                    if (state[x + r, y + c] == value)
                        return true;
                }
            }

            return false;
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            e.Graphics.DrawImage(img, 0, 0);
        }

        [STAThread]
        static void Main(string[] args)
        {
            Application.Run(new Program(w: 500, h: 500, f: 2, p: 5));
        }
    }
}

Python: 

L = 15

initial_trees = 0.55
p = 0.01
f = 0.001

try:
    raw_input
except:
    raw_input = input
    
import random


tree, burning, space = 'TB.'
hood = ((-1,-1), (-1,0), (-1,1),
        (0,-1),          (0, 1),
        (1,-1),  (1,0),  (1,1))

def initialise():
    grid = {(x,y): (tree if random.random()<= initial_trees else space)
            for x in range(L)
            for y in range(L) }
    return grid

def gprint(grid):
    txt = '\n'.join(''.join(grid[(x,y)] for x in range(L))
                    for y in range(L))
    print(txt)

def quickprint(grid):
    t = b = 0
    ll = L * L
    for x in range(L):
        for y in range(L):
            if grid[(x,y)] in (tree, burning):
                t += 1
                if grid[(x,y)] == burning:
                    b += 1
    print(('Of %6i cells, %6i are trees of which %6i are currently burning.'
          + ' (%6.3f%%, %6.3f%%)')
          % (ll, t, b, 100. * t / ll, 100. * b / ll))
                

def gnew(grid):
    newgrid = {}
    for x in range(L):
        for y in range(L):
            if grid[(x,y)] == burning:
                newgrid[(x,y)] = space
            elif grid[(x,y)] == space:
                newgrid[(x,y)] = tree if random.random()<= p else space
            elif grid[(x,y)] == tree:
                newgrid[(x,y)] = (burning
                                   if any(grid.get((x+dx,y+dy),space) == burning
                                            for dx,dy in hood)
                                        or random.random()<= f 
                                   else tree)
    return newgrid

if __name__ == '__main__':
    grid = initialise()
    iter = 0
    while True:
        quickprint(grid)
        inp = raw_input('Print/Quit/<int>/<return> %6i: ' % iter).lower().strip()
        if inp:
            if inp[0] == 'p':
                gprint(grid)
            elif inp.isdigit():
                for i in range(int(inp)):
                    iter +=1
                    grid = gnew(grid)
                    quickprint(grid)
            elif inp[0] == 'q':
                break
        grid = gnew(grid)
        iter +=1