btw the spektrums never get interference thats basicly why everyone has one lol
And now that everyone is on Spektrums, all the oldies who still use 40MHz (like me ) almost never suffer frequency clashes and I've never had a major problem with interference.

Welcome to the forum Nick. Sounds like you've got a good grounding, knowledge and resources (CAD, CNC etc) to hand which is a pretty good start even before you've designed or built your bot. Where are you studying your degree, and what year are you in? (just slightly off topic, as I'm studying for a Mech Eng degree)

Although plunging straight in to building a robot with a weapon for your first attempt quite doesn't work out for some people, it sounds like you're competent enough to take a sensible moderate approach to it, rather than jump in and try to make your weapon super-awesome-better-than-everyone-elses. After watching Robot Wars as a kid too, I finally got into the sport (about five years ago) with a basic wedge and while it is an easy starting point for beginners, they do get a bit dull to operate after a while!

As for your weapon choice, where are you based? Because that could have a bit of an effect. I would definetly recommend a spinner as they're so much fun, but as you are aware, they can only operate at a few events a year. If you're based in what seems to be the nucleus of roboteering (mid-England, Birmingham and surroundings areas), you may be better off leaning towards an axe or crusher as you'd be able to run these at both Roaming Robots and Robots Live events (plenty of them running each year) as well as the full combat events thereby getting regular use out of your machine. You could even go that step further and build modular weapons units, so that you could run an axe or crusher at most events, and then whack a spinner mechanism in there when the full combat events come around.

As for advice on the wepaons themselves;

Spinners: while you must take care working and operating them, I wouldn't say they're actually that difficult to make. Basic parts are a motor to power it, a means of transferring the motion from the motor (timing belts and pulleys, gears, chains or friction), the spinning mass itself, a shaft for it to rotate around, bearings to improve efficieny, and a frame to hold it all together. While there are other little bits and pieces to help fine tune it (tensioners etc) they can vary from bot to bot and is something you're bound to come across and form a solution to it in your own bot. For frames, aluminum and steel are the most obvious ones and they can usually withstand the loads from spinner impacts, but plastics work very well too. I use 20mm thick Nylon 6 on my robot and will be changing down to 12mm polypro for the rebuild. Rather than bending from impacts and stresses, they elastically deform to dissipate the energy and then resume their original (or pretty close to original) shape. They're also cheap and very easy to work with.

Axes: the two most successful axes without a doubt are Little Hitter 2 and Basher. However they both utilise CO2 and since you're keen to stay clear of that until you've gained a bit of experience and advice, the next best method of power is electric. Simply a motor connected by a chain and sprocket setup (the most popular choice) to the axe and you have yourself a weapon. Its similar to a spinner in the sense that you need an axle/shaft for it to run on, but you'd need a larger gear reduction to decrease speed and increase torque (compared to a spinner). I've not made a proper axe weapon myself so I don't really have much to add to the above info but there are plenty of others who will be able to expand on the subject. This Australian Robowars Wiki article may help too: http://www.robowars.org/wikka/ElectricAxeWeapons

Crushers: hydraulics have not yet featured in a fully working featherweight but as Alex has mentioned, there is a European featherweight that is due to have working hydraulics and I believe a UK roboteer is working on creating a micro-hydraulic system from scratch. Until then, the most popular powerplant for a crusher is an electric actuator. Alex has a gem of an actuator in his robot that gives 700kg of tip crush; I have an actuator that will give 400kg of crush. Anything less than this any you'd be struggling to pierce an opponent's non-metal armour (metal armour these days is superbly strong and thick and most likely won't get pierced by a feather crusher, only bent at most).

If you can find an actuator that gives somewhere between 600kg and 1000kg then you've got a good force for a crusher. Downsides are that most actuators of that rating are quite large and may have to be partially exposed in order to save weight (http://www.teamdragon.org.uk/html/dragonsclaw.html). The other thing with crushers is to make sure they don't destroy themselves! Strong bulkheads running the length of the robot to add rigidity and strength and hopefully stop the baseplate from bending, strong shafts or axles at the pivot points, and a strong claw construction will all be essential - lots of strong basically

If you use MSN, feel free to add me lenny_1024(AT)hotmail.com. Many other roboteers use MSN too and its a useful way to bug other roboteers for useful advice

Finally, best of luck for when it comes to building your robot