For harassers, you can't beat the Yellowstone shuttles. They have a tetryon warp plasma (eject warp plasma) and a tractor beam 3. They are armed with phaser beams and chroniton torpedoes.
The elite delta flyers are useful for depleting or getting through shields with tachyon beam 3. They have transphasic torpedoes and phaser beams.
The Elite peregrine fighters are ok, since they have quantum torpedoes.
The elite scorpions have high damage if they can stay alive, thanks to the high yield plasma torpedoes. Though those same torpedoes are targetable and can be destroyed unlike the peregrine's quantum torps.
The type 10 shuttles (which I have never used) are tougher than fighters, and you can launch up to 6 of these. Their damage is lower than other pets, but would be good for absorbing faw spam and general harassment. They would also be good for soaking up mines and high yield torpedoesI suppose.