You can use hunterfly / dracula / sniper cecil on following weapons :
leech weapons katar class :
specialty jur [4] usable since you started become assassin (level prereq : 1)
Elemental Katar [3] (icicle, dusty, blaze, wind) usable at lvl 55 and above
Krishna [2] usable for sinx at lvl 50 and above
Chakram [2] usable for sinx at lvl 50 and above
Crimson Katar [2] usable at lvl 70 and above
Thanatos katar [1] (HP&SP) usable for gx lvl 120 above mainhand
leech weapons dagger class :
knife [4] or main gauche [4] as offhand weapons, usable since you become thief (level prereq :1)
valk knife [4] as offhand weapons, usable starts at lvl 70
scalpel [3] as offhand/mainhand weapons, usable starts at lvl 55 transcendent class
Crimson Dagger [2] usable at lvl 70 and above
Thanatos Dagger [1] as offhand/mainhand (HP&SP), usable for gx lvl 120 above
leech weapons axe class :
orcish axe [4] as offhand weapons, usable since you started become assassin (level prereq : 3)
leech weapon sword class
Twin Edge of Naght Sieger Red/Blue [3] as offhand / mainhand weapons, usable since lvl 75 transcendent class
Saber [3] as offhand / mainhand weapons, usable starts at lvl 27
Solar Sword [1] (HP) usable starts at lvl 40
Crimson Sabre [2] usable at lvl 70 and above
Headgears Top : Magician Knit Hat (SP against undead race enemies), Pirate Folly (SP), Oni Horns (HP), Cursed Book (HP Dominant & SP), Rideword Hat (HP Dominant & SP), Vanargand Helm (HP & SP Dominant)
Headgears Low : Tengu Scroll (HP), Blood Sucker (HP)
Armors & Armor cards : Evil Dragon Armor (HP&SP), Earth deleter card (SP)
Garment & Garment Cards : Red Lotus Stole (SP), Nidhoggur Shadow Garb (SP), Undead Knight M (HP), Undead Knight F (SP)
Pets : Succubus (HP), Incubus for (SP)
Shadow Equipments and costume : Malicious Shadow Set, Costume garment SP absorp