I think one needs to be very careful with "disabling" effects in weapons. Completely freezing someone, regardless of how short the period, is comparable to forcing game hangs, which I don't think wold be fun even if it is a game mechanic. "Oh, I cant do anything now, fun", is something to be avoided.
Hence I'm strongly opposing freezing, and also for similar reasons mildly opposing slowing players as a common occurrence via a weapon.
Random (crappy) ideas not affecting movement:
- freeze/weakening effect makes other weapons (except fire?) make more damage, i.e. it's a support weapon, freezer+pistol is more effective than freezer alone
- Chain lightning which jumps if second opponent is less than a certain distance from opponent being fired at
- Lightning beam not interrupted by opponents, (...not by walls?), still range limited.
- Beams of lightning extending in multiple directions from gun (half cirlce? secondary fire candidate?)
- Cloaking field/other fancy non-combat ability for secondary fire (may go against the ability-sparse style of RE?).