If you read the unlocking weapons hack at https://www.mpgh.net/showthread.php?t=1, then you already know how to get the AK-47 and the desert eagle. This will show you how to get the SSG for the scout, and a P90 for the medic and engineer class. I also have some key parts of the packet below, if you want to play around with it on your own.

Alright, start up warrock and make a room for yourself. I like to make it a secret room with a password, but it's your call.

Anyway, on the first spawn screen, press the scout tab and right click on the sniper rifle to unselect it. Start recording packets in WPE Pro (https://www.mpgh.net/showthread.php?t=1 if you don't know how) and re-equip the sniper rifle by clicking the empty slot, then the picture of the sniper rifle on the right. Stop recording packets, and add the one that's 22 bytes long to your send list. Start editing it, and look at the second group of two characters on the second line. It should say F6. Change this to F7, check the packet, set the send list to use the right socket ID, and send the packet once. Bam, you've got an SSG instead of your normal sniper rifle.

Now click the engineer tab on the top, and right click the machine gun thing to unselect it. Start recording packets and re-equip the machine gun thing. Stop recording, and add the 22 byte packet to your send list. Edit it so that the second group of two characters on the second line, which should be F2, is F1 instead. Check the packet and send it once. This should give the engineer the P90. Now start editing the packet again, and change the 9th group of two characters on the first line, which should be F3, to be F2. Send the packet again, and the medic should have the P90.

There you have it. This is a little simple, I know, but the weapons hack in the official stickied topic only mentioned two weapons, which might give people the impression that that's all there is. If you want to play around with the equipe packet, here are some key parts:

First Line, 9th byte: Which character class you're equipping
F0: Combatant
F1: Scout
F2: Medic
F3: Engineer
F4: ???
F5: ???
F6: ???
F7: Heavy Weapons
I have no idea why F4-F6 aren't real classes. This could be interesting if you started messing with the spawn byte, maybe some unreleased characters?

Second Line, 4th byte: Slot you equipt into
F0: 4th slot
F1: 3rd slot
F2: 2nd slot
F3: 1st slot
No idea what the 5th-8th slots are. Maybe counting down from FF?

Second Line, 2nd Byte: What Weapon you Equip
The numbers here vary based on some unknown part of the packet, but usually F1&F2 are the two choices (the sniper rifle is F6 and F7), if there's more than one.

There's some part of the packet I don't know that indicates what class' weapon the second byte on the second line indicates. For instance, taking the packet to equip a grenade and changing the character class it will say "this weapon cannot be equipped by this branch of the army" or something, even if the number in the second byte of the second line is the same as in the packet to equip the normal 4th slot weapon for that class. I think this is the key to equipping different class' weapons on other classes, so any help on this subject would be appreciated.