Mostly pre-war equipment, though most rapidly figured out it was less than effective against Imperial laser weaponry. Most used simply to carry equipment and provide some protection against spalling from missed laser shots.

Pre-war radios using one time pad ciphers as modern human encryption methods prove useless against a species with widespread and effective quantum computing.

Hand delivered messages.

Dead drops.

Pre-war night vision devices and thermals.

Some jamming gear proves effective against Imperial systems, though it is usually rapidly located and destroyed. Typically used in a tactical role against individual Imperial patrols.

Most pre-war technology with connectivity is found to be compromised within a year of the start of the occupation. The various measures taken by the worlds governments previously to spy via such devices or even the companies controlling them as a means for targeted adversiting where rapidly taken up by the Imperium. They provided a means of direct observation either via the activity of the users or using them as listening devices. Some are 'neutered' with wireless connectivity removed or outright abandoned.

Full caliber rounds and antimaterial weapons prove to be the only real thing to be effective in tactical situations against Imperial ground troops. Weapons of an intermediate or pistol caliber, while they can defeat the armor with a sustained burst at close range, usually leave the user vulnerable and often get them killed.

Various pre-war rocket and missile systems survive Imperial efforts at their confiscation and destruction.

MANPADs, even old systems such as the SA-7, prove effective when used in volleys against Imperial low flying aerospace craft.

Point defense on Imperial ground vehicles force the use of volleys of unguided or guided antitank munitions, the latter of which are rapidly exhausted due to their expense and lesser number.

'Hellfire' 12-gauge slugs, created via stolen Imperial fabricators these are effectively miniature HEAT rounds (high-explosive shaped charges). While short range they provide the various resistance groups with a piece of ammunition that can kill an Imperial trooper using any readily available shotgun. They are however costly to produce and are in limited number.

Captured laser weapons, their security 'cracked' and allowing anyone to pick up and use them, power cells however remain a finite resource and depend on bribery, thievery, and battlefield looting to maintain their stocks.

Crew serve railguns, fashioned in cottage industries out of sight and mind of the occupation. Finicky and powered by alien battery tech, but devastating when properly positioned.