Angled or straight jack plugs?
It depends on what type of guitar you play. Generally speaking, you should run a straight jack into your amp’s input. Angled jacks can be useful, though, when using guitars where the input is mounted flat on the top of the guitar – such as a Gibson Melody Maker.
A straight jack protruding from a top-mounted input can be easily knocked, which can crack your scratchplate if the blow is hard enough. An angled jack should be much less vulnerable. However, angled jacks usually won’t fit traditional Tele inputs, which are recessed into the body.
You may also want to use a slender, straight jack when plugging into Strats and similar guitars with deep-set, angled inputs.