Loophole

What loophole in a video game did you exploit the crap out of?

In an F1 management simulator you could fire and re-hire drivers and other staff. Every time someone was fired, including by players, their market value went down and you could hire them with lower pay.
The hiring/choice of staff was done for whole season between seasons, so you could get the best people available for minimum wage. Only downside was that they would immediately quit after the season and other teams would grab them, but there were enough good drivers and mechanics to keep doing this.


In freelancer game Wing Commander: Privateer there were always bunch of randomized missions in each (regular) planet. A common type was to patrol some or all nav point in the system or kill enemies in certain nav point or somewhere in the system.
As you could take up to three missions at once, you could usually find three that were essentially the same: like "patrol nav 2", "kill pirates in nav 2" and "patrol all 3 nav points". So you would be paid for three missions when doing one.
If there weren't three overlapping missions available, you could just leave the planet and go right back to randomize the missions again, on second or third time it usually worked (for most of game, once you had unlocked more missions).

Although you could argue that was a designed element rather than a real loophole.