Gravity Crash

Only one planet, Aquoort (4.5, in the Noort system), contains all 3 weapon pickups. Besides that, they are normally spread across planets (never more than two on the same planet), so if you do this early you’ll need to stockpile them and complete the planets in as few shots as possible. Once you have all three pickups at the same time, fire once and the trophy will pop.

There are two places where you can get this the easiest:

System 4 (Noort)
This is probably the easiest way, if you can make yourself wait until later in the game. The fifth planet in this system, Aquoort, contains all three pickups needed for this trophy. The side and 3-way pickups are above water and easy to get, one on the right side in a cave, the other at the far top left of the map (near the node). Don't grab them immediately, though. Kill all the enemies you can in between and figure out the path through the water maze in the bottom left part of the level. You'll need to hit a switch in the bottom left room in order to get access to the top left room that holds the artifact and the rear shot. Once you do that, get the rear shot, make your way back out of the maze and then pick up the other two (side and 3-way). You can do it the opposite way, but make sure you know the way through the maze first, as you will need to spend a lot of shots on the buttons that open the gates to get to the rear pickup.

System 1 (Basix)
Since you don’t need to shoot a lot at the beginning and the levels are easy, the first system is also a good place to get this. It will have to be done in Campaign mode so that your weapons carry over from planet to planet. Remember, fire as little as possible once you start collecting the pickups. Get the 3-way shot on Eazia (1.1), then get the side shot on Zeeta (1.2). After that you can do either Vectora (1.3) to replenish 3-way shot or Effendia (1.4) to replenish side shot. Rear shot can be found on Abyssia (1.5). When you get there you should have at least 20 shots for the other two at the minimum.