Kevlar/nomex flight suit, a couple of peripherals to determine vitals (limb fractures, bleeding, puncture wounds, EKG monitors… etc)
For guns, I would carry one of the following combos:
1) A fuck huge (think at a minimum .338 Lapua ) rifle with a decent scope and a steady diet of exotic ammo. Secondary weapons of a shortened shotgun (Serbu Shorty short, with AP slugs), and a suppressed machine pistol along the lines of an MP9 or smaller (folding stock, pistol grip, foregrip, threading for suppressor)
This would be for someplace all desert-y or perhaps a few temperate forest type climates.
2) An upper mid-sized carbine. NOT 5.56, but something more like .45-70 or 308. Short and mag fed with a fun switch preferred. Optics required. Lasers a bonus. Expanding or explosive ammo required. Incendiary or APIT ammo is a bonus. Underslung grenade launcher also a must. Shotgun shell nades a bonus.
Sidearm would be an SMG along the lines of a PPSH. basically an LMG in a pistol caliber package and as small as possible. For grenades, I'd want something like an M14 or a bunch of M67s. Maybe WP.
This would be for jungles, because fuck jungles. FUCK jungles. And fuck reloading in jungles. And fuck not being able to light everything on fire.
3) Flame thrower, semi-auto mag fed shotgun (or a Milkor with the Beehive shells because fuck you and your mother you alien bastards) and a .45/9mm/.357 SIG handgun with APIT. Night vision goggles and a crate of goddamn glowsticks. As a backup, a Serbu shorty with AP slugs.
Caves. Anything that even remotely resembles a cave. A dark planet that doesn't have a normal daylight cycle.
4) the shortest, lightest possible LMG. Backup guns inclusive of a serbu shorty with APIT slugs, a P90, and fucking flood lights.
Marshes or swamps. Alien crocodiles need many boolit, or AP rounds.
5) a suppressed, short length, intermediate carbine, with an underslung grenade launcher, preferably in .300BLK and a 13.7"~ barrel, with a CQB type optic, and access to both subs and supers. Side arm of a threaded CZ-75 or CZ P-09.
Space pirates. Boarding and repelling boarders.
Fucking cunts.
Basically, I intend to prioritize armor penetration and volume of fire as much as possible, and if all else fails, I will literally kill it with fire.
I'd hate to encounter some kind of carnivorous alien rhino skinned dinosaur and be shooting it with a 5.56 carbine or even a .308.
Teams work in a minimum of two guys, with one guy shooting high volume of fire to give other guy time to pull out big scary hole puncher, or serbu.