The Debug builds run with cheat mode enabled by default, here are all in-mission cheats: (note how they all require the [~] key.)
~-Shift-C Toggle availability of countermeasures for all ships.
~-K Kill targeted ship.
Note: Actual function is to inflict 100 000 points of damage to target ship. Bypasses ship-guardian invulnerability.
~-Alt-Shift-K Do 10% damage to target.
~-Shift-K Destroy targeted subsystem on target.
Note: reported as now working in 3.6.16
~-Alt-K Do 10% damage to yourself.
~-I Toggle self-invincibility.
~-Shift-I Toggle invincibility of your target.
~-O Toggle Descent-style physics. This means that you have no inertia or momentum, your afterburners do nothing but jerk you to a halt instantly, and you can slide with the keypad +, -, 1 and 3 keys.
Note: This does not appear to work in Retail FreeSpace 2, but has been re-enabled by the SCP.
~-W The player has infinite weapon energy and missile ammunition.
~-Shift-W All ships have infinite weapon energy and missile ammunition.
~-C Toggles player collision detection, allowing you to pass through objects and ships.
~-U Launch an asteroid from the player's position.
Note: prior to 3.6.16 (including retail), this will cause a crash if there is no asteroid field in the mission.
~-G Mark all primary goals complete.
~-Shift-G Mark all secondary goals complete.
~-Alt-G Mark all bonus goals complete.
~-9 Cycle forward through ALL secondary weapons, including the Shivan and Vasudan ones and cruiser/destroyer only ones. This includes the Fusion Mortar, an anti-capital ship turret weapon that does not require a lock to be fired.
~-Shift-9 Cycle backwards through ALL secondary weapons
Note: This does not appear to work in Retail FreeSpace 2, but has been re-enabled by the SCP. In FreeSpace 1, it also for some reason allows
you to access primary weapons for your secondary banks.
~-0 Cycle forward through ALL primary weapons, including the Shivan and Vasudan ones and cruiser/destroyer only ones. This includes the Shivan Super Laser, AKA the Lucifer Weapon. This can kill a Demon at 6 kilometers in only a couple of shots, and can function as a sniping weapon in a dogfight to kill enemy fighters in a single hit.
~-Shift-0 Cycle backwards through ALL primary weapons.
~-r Issue Rearm order for current target, or player if there is no target.
Note: Doing this on an object with no engines will cause the game to bug up.
Mod-specific cheats aren't really a thing I'm afraid.
EDIT: kinda got Ninja'd but this should help nonetheless.