Communities like Pixel Gun X or PG3D Private Server offer custom servers where everything is unlocked for free. You cannot play against official players on private servers, but you can test every weapon in the game against your friends. This satisfies the "unlimited gems" urge without breaking the official rules.
For the sake of completeness, users often search for mods on: pixel gun 3d mod menu pc free
Verdict: Even the "safest" mod menu is temporary. Expect a ban within 1–7 days. Communities like Pixel Gun X or PG3D Private
If you want the precision of an aimbot, download free aim trainers like Aim Lab (Steam). Practice for 10 minutes before playing Pixel Gun 3D. A skilled mouse-and-keyboard player on an emulator already has a massive advantage over mobile touch-screen users. You don't need hacks; you need muscle memory. Verdict: Even the "safest" mod menu is temporary