I was thinking that a pack with futuristic (but not super-futuristic) weapons would be really cool. Ladios's laser pack is somewhat bland and I think it would be cooler to have more complex weapons.
Energy: All weapons would use a certain amount of energy, displayed as a bottom print (along with health). If you drop below 50% energy, it will regenerate at 1% per second until you are back to 50%. This is so that you will never be entirely screwed out of firing, but will mean you have to find energy to fire the more powerful weapons.
Batteries: Similar to the health pickups (hopefully styled similar to the TF2 pickups), you would be able to find batteries as items. Values would be configurable as a preference, but default values could be 25 for the small battery, 50 for the medium, and 100 for the large. Also comes with a portable battery, that can be stored in your inventory and used an any time.
Shield: Uses the player's energy to provide a force field to protect them. While active, their health will not go down at all. Every point of damage decreases the player's energy by 1%. Also, energy will not recharge while active. Once the player's energy drops below 25%, the shield will short out and will not function again until their energy is above 25%. Requires 5s to power up.
Tier 1 Weapons: This weapons would be balanced against one another, but weaker than Tier 2 and Tier 3. They're essentially brown townogs of a pistol, machine gun, shotgun, and sniper rifle.
Proton Popper - Your basic pistol. Fires red projectiles (modeled ones, like in the Quake-Like pack, not just emitters). Deals 5 damage per shot, uses 1% energy, medium range, low spread, 1s recharge time. Semi-automatic.
Electron Beam - A fast-firing but weak weapon. Fires a continuous jet of yellow projectiles. Deals 1 damage per particle, 0.1% energy per particle, short range, medium spread, and 0.1s recharge time. Fully automatic.
Neutrino Cloud - Fires 20 purple projectiles at once that have significant knockback. Deals 1 damage per particle, 5% energy per shot, short range, very high spread, and 5s recharge time. Semi-automatic.
Neutron Launcher - Fires a medium blue projectile. Deals 50 damage, 10% energy per shot, very large range, no spread, 5s recharge time. Semi-automatic.
Tier 2 Weapons: These ones are a lot more interesting, with actual mechanics as opposed to fancy guns.
Nucleic Cannon - Fires a flashing magenta and cyan explosive projectile. Deals 30 damage at explosion center with fading damage as you move away, 10% energy per shot, medium range, low spread, 5s recharge time. Semi-automatic.
Tesla Coil - Creates a stream of homing white sparks. Deals 5 damage per particle, 1% energy per particle, short range, medium spread, 0.1s recharge time. Fully automatic.
Electric Overloader - Surprisingly, nobody installed any fuses on the energy packs, so they can be overloaded quite simply. While this shot is relatively weak, it has high knockback and causes the enemy to initiate a tumble. Not only that, but the stun effect (not the damage, though) penetrates shields! However, it recharges the enemy's energy by 10%. 10 damage per shot, 20% energy per shot, short range, low spread, 5s recharge time. Semi-automatic.
Muon Stream - A powerful stream of muons, which are like electrons but cooler. Deals 4 damage per particle, 1% energy per particle, medium range, no spread, and 0.25s recharge time. Fully automatic.
Tier 3 Weapons: Time to get out the big guns. These colossal cannons will wreck your face very quickly, though they have very taxing energy costs.
Antimatter Reactor - Fires a large black projectile with a white trail, and has gravity. Deals 200 damage at explosion center with fading damage as you move away, 75% energy per shot, low range, low spread. It's semi-automatic with 30s recharge time, but it doesn't matter if you blow yourself up with the gravity. Not only that, but you cannot recharge enough energy to fire it again naturally.
Fission Shot - Fires 10 red and green projectiles at once that split into 5 other particles on impact, and gravity applies. Deals 10 damage per particle (both types), 50% energy per shot, medium range, very high spread, and 20s recharge time. Semi-automatic. Can deal a lot of damage in a crowded area, but probably won't get you very far in an empty room.
Tesseract Launcher - Fires a translucent, multicolored cube that bounces off of walls at twice the speed they hit them with - does not get destroyed on impact with a player, but despawns after a certain amount of time. Deals 50 damage, 30% energy per shot, long range, N/A spread, and 10s recharge time. Works wonderfully in confined spaces.
Tau Beacon - An immensely powerful stream of talons, which are like electrons but really, really strong. Deals 10 damage per particle, 5% energy per particle, medium range, no spread, and 0.25s recharge time. Fully automatic. It's got nice DPS, but good lord you're going to run out of energy in a mere 5 seconds.
Values may need to be tweaked for balance. Hopefully this gets done, but I would't be surprised if it isn't. It's quite a large request, and I apologize.