[Otaku]

What to do:
-Mill your chassis. This might not come in to the minds of rookie teams or people who just haven't done it, but it can shave off a lot of weight, oh, and it can even make handles on your robot (but I don't suggest that).
-Speed holes in week 5/6. Cheese-grater robots are still robots.
-Calculate everything. You won't need to make speed holes if you figure it all out beforehand and get it taken care of.
-Use thinner material, or use it smarter. I'll leave this for you all to figure out.
-Lop off excessively long shafts or bolts. It might add up to that crucial pound or two.
-Use lighter parts. Aluminium sprockets, thinner gague wire where thick stuff isn't needed, etc.
-Plastics are your friends. Lexan/Polycarbonate/Plexiglass instead of actaul glass (why would you want it?) or aluminium.
-Minimize Pneumatics. They're heavy and ineffecient.
-Minimize Chain. It might not weigh a bunch on it's own, but it will add up.
-If all else fails, Nitroglycerin. Sure, you might not have anything competition-worthy afterwords, but you'll be under the limit.

Tools you will need:
-Drill
-Angle Grinder
-Dremel
-Nibbler (Maybe?)
-Mill (CNC, Precision, or otherwise)
-Files. Lots of files. Straight files, round files, cylindrical files. Single cut. Double cut. Bastard.


That should help. Oh, and good doses of common sense will help you out, too.