[Suicide Junkie]

I like the idea of removing auto-fire ability from the point defense in SE4. Then you never know what will happen.

For SE5, there is a nice option for leaky PD utilizing the poission distribution.
1) Set PD guns to -999% to-hit. (IE: guarantee the 1% hit chance despite all bonuses)
2) Set reload time to ~50ms
3) Set the damage to 999
4) Set the PD projectile speed very high, or make it a beam.
5) Disable the PD animations, or at least make them short and simple; flak bursts perhaps.
6) Disable the sound effects, or possibly make them VERY VERY quiet so that 100 of them overlapping isn't speaker-blowingly loud.

Improved PD potency comes from increased range and additional PD guns.
Improved PD penetration comes from increasing seeker speed and larger volleys.

You get 20 shots per second from each PD gun, so the longer the seeker is in range the better your chances.

There is a small chance that you won't shoot down any missiles, but there is also a small chance you will shoot down lots of missiles with just one PD gun. The more the merrier, but nothing is guaranteed, and you get a nice poission distribution of missile-kills.