SI idea, the Spiker

[Dr Ampersand]

Not sure about appearance but it's a SI who can shoot out many small spikes over a very large area. The spikes are airborne(think air propagated seeds except they're spikey and they have an energy store inside so rather than just falling they actually hold themselves up in the air by spinning themselves before falling) and come towards you. They do damage over time (but less than the spitters) and if you're nearby the cloud of spikes will slowly come towards you (though how that happens doesn't really matter, could be due to survivors breathing or the seeds could be attracted to the smells of a non-infected human). The cloud lasts longer than spitter spit but can be destroyed by molotovs and explosions

This would be the L4D equivalent of an area denial SI except it'd work better during hordes and crescendos when people are in the same place for a long time.

tl;dr: floating spikes, damage over time they come towards you.

[Stagger Lee]

I remember that someone already made a suggestion for a S.I. like this that throws spikes. What's weird is that people kind of liked it but Valve didn't use it while other ideas that people initially didn't like, Valve used for L4D2.

[Xezium]

Yeah, this same thing has come up oodles of times in the past.

[JackieChan]

Originally Posted by Stagger Lee

I remember that someone already made a suggestion for a S.I. like this that throws spikes. What's weird is that people kind of liked it but Valve didn't use it while other ideas that people initially didn't like, Valve used for L4D2.

I think their main concern was to combat the whole corner camping. Combat it they did... even if their ideas weren't entirely their own.