Size 1, size 5, size 6, size 24, size 40 and size 50... Hm, where should I put the vote?
I use a lot of different missiles. Size 1, of course, makes a good spam weapon, size 5 is the mainest of main calibers, size 6 for long-range missiles, 24 for MIRVs\torpedoes, sz40 is for heavy torpedoes, and 50 is for mines.
Of course, since my modus operandi is "speed is everything" I tend to have rather short-ranged missiles. They do have good speed and to-hit chance though, and I have specialized LR missiles\MIRVs\torpedoes when I need them.