One tool I won't use a cheap version of is an angle grinder. I had cheap ones in the past, one burst into flames in my hands, no smoke straight to flames and it burnt for 20 mins afterwards. The second one, locked up whilst cutting, ripping the machine out of hands and shattering the disk which cut a three inch cut across my scalp. So I have DeWalt cordless 18v and FlexVolt an AEG 9 inch and Bosch 9 inch. The Bosch works out quite a cheap option as it comes with 2 diamond blades (£26 each) and a quick fit collar as well as the conventional one.