The title pretty much says it all, but I do want to elaborate a bit on my reasons for choosing the flechette cannon. First, it's rarely used. Only a few people have been able to use it effectively in combat. Second, it's hard to hit anything at long range.

This provides a defense against flares at the cost of a gun port for a more generally effective weapon, without being overly powerful (if you manage to hit a flare, it will probably be close enough that you'll get some splash damage).

The other use would be in an anti-swarm capacity. A fast ship equipped with flechettes could intercept and destroy swarms launched at capships. In certain situations, it would also be useful for anti-griefing (intercepting swarms fired by griefers).

Good idea. Gives them a less obscure role.

Seconded errr [stamp of approval] errr I WANT TO HAVE MY POPCORN AND EAT IT TOO.

Thirded [stamp of yummy approval] mmm popcorn

detonating ordinance I've wanted for a looooooong time. if it must be done with the flechette.... so be it.
Approved!