One of my favourite things to do was play single player against a particular AI that would spam out hundreds of buses. It would always quickly take the lead, so I'd set up my own bus routes, then order all my buses to stop in the middle of the road at once.
This would lead to massive gridlock, effectively denying the AI profit while its operating costs dragged it to bankruptcy. When it went bust, I'd buy out the company, then allow my (now) hundreds of buses to move again!