The type of familiar you're going to summon with the Find Familiar scroll (if your main character is a magic user) depends on your alignment:

LG, NG = pseudo-dragon
CG = fairy dragon
LN = ferret
TN = rabbit
CN = cat
LE = imp
NE = dust mephit
CE = quasit

They are all pretty balanced in various ways, so don't worry about getting the rabbit (it, for instance, is super-fast and has a very high Magic Resistance, making it an interesting scout).

More details:

Lawful Good - Pseudo Dragon, -2 AC, 24 HP, 50% magic resistance, renders victims unconscious, casts Blur

Neutral Good - Pseudo Dragon, -2 AC, 24 HP (same as above)

Chaotic Good - Fairy Dragon, 4 AC, 24 HP, 32% magic resistance, casts Invisibility 10' Radius & Mirror Image 1/day

Lawful Neutral - Ferret, 0 AC, 24 HP, 50% magic resistance, 75% Pickpocket, 40% Stealth, 20% Detect Traps

True Neutral - Rabbit, -4 AC, 16 HP, 50% Detect Traps, 30% Stealth,
75% resistance to fire, cold, electricity

Chaotic Neutral - Cat, 0 AC, 24 HP, Pickpocket, 99% Stealth, 50% magic resistance

Lawful Evil - Imp, 2 AC, 18 HP, Polymorphs, 25% magic resistance

Neutral Evil - Dust Mephit, 6 AC, 24 HP, Casts Glitterdust 2/day, 10% magic resistance

Chaotic Evil - Quasit, 2 AC, 24 HP, Casts Horror, 25% magic resistance

Top