Singleplayer is one of the best things for doing that thanks to the fact that you can give yourself cash and beam yourself around bases.
Someone here had made a very nice thread compiling a lot of them into one to showcase them, but I can't remember who and where unfortunately.
Found a couple of threads but they seem outdated or not really clear. Would've been cool to have a wiki page for them but yeah, it's a wiki, so I understand.