Like imagine if over time your character 'charges up' a white gun in their inventory. Takes about a minute to charge one. Once charged, you can switch to it and it'll do blue style damage for one clip. Then it can't be charged up again for around 20 minutes.
Charged guns are accessed, say, by holding down the grenade button - it'll switch to the gun and when you reload or empty the clip, it'll go back to the weapon you were using before.
The thing is, then every gun you pick up you'd actually use!
Instead of them being pointless busy work trash items to sell.
Because that's what they are - pointless busy work.