Hi,
you can generate an infinite amount of resources when you permanently colonize the same planet over and over again with the Gigalord. When colonizing a planet you get 2.5k of every resource, no matter which colonisation ship is used. But the Gigalord stays on the planet and if you only build until the spire and fly back to the orbit of the planet you are left with a lot of resources.
Calculation:
You get 2500 metal, 2500 minerals and 2500 vespene in the moment the Gigalord colonizes a planet.
Building the Incubator to lvl 3 and then spire to lvl 1 costs:
Incubator 1: 50 metal, 5 minerals
Incubator 2: 80 metal, 8 minerals
Incubator 3: 128 metal, 13 minerals
Spire 1: 800 metal, 100 minerals and 250 vespene
Further you have flight costs of 680 vespene to move the Gigalord from Orbit down to planet and back up.
Finally you generated:
2500 - 50 - 80 - 128 - 800 = 1442 metal
2500 - 5 - 8 - 13 - 100 = 2374 minerals
2500 - 250 - 680 = 1570 vespene
You can do this over and over again on the same planet with as many slots you like.
It takes me 7.5 minutes for 1 flight. This means a total of roughly 20 minutes including building the necessary buildings to get the Gigalord back up. So I can do this 3x per hour which means I get per hour per Gigalord and planet:
1442 * 3 = 4326 metal
2374 * 3 = 7122 minerals
1570 * 3 = 4710 vespene
This is basically the production of a semi-developed planet and if someone gets his Gigalord early it's even more than a production of his planet. (In late game it's probably not enough anymore to cope with fully developed planets.)
Further if you use 30 seconds more and move the Gigalord from one planet to the next planet then you also can collect the resources that spawn on every planet every 6 hours which would increase the output for each planet by roughly x1.5 to x2.0 if the person is lucky.
I think all colonisation ships that stay on the object after colonisation should not grant resources because this is exploitable.