So... fitting a mini fan today... decided a nice square hole would be perfect... well - rectangular with rounded corners.
My tools: drill, 14mm drill bit, junior hacksaw, file
Time take - 3 hours
Result - PERFECT (for me.... could be neater, but hey :p)
Photos to follow... but this was really painful. Used the drill around the outside but with inch thick wood it took ages just to get through each time. Finished the opening with the junior hacksaw and then spent the remaining two and a half hours filing it to size.... All because B&Q didn't have any of the cheap to mid-range jigsaws left... only the ones near £100 remained :p