Best Sources of Exp/Drop Buffs

I'm gonna prioritize stuff you can get ingame, and stuff that lasts longer. Separate spoilers for stuff that stack; will mention stuff that doesn't stack inside the spoiler. So basically the question is, what else is out there?

 Big Spider Familiar: 60% drop

Drops from the relevant monster at a low rate.
Lasts about 2 hours after being summoned; permanent.

Alternatives:
Mutant Pig Familiar (60% drop) - drops from the relevant monster
Wolf Underling (100% drop) - can't be obtained ingame
Easter Egg Buff (100% drop) - can't be obtained ingame
Weapon & Armor Store Part-Time job (30% drop) - lasts 10 min per hour logged out.

 Greed Pendant: 20% drop

Drops from the boss in Monster Park Extreme at a low rate.
Permanent.

 Inner Ability: 3%/8%/13%/18% drop

Rare/Epic/Unique/Legendary ranks. Obtain by recirculating.
Permanent.

 Legendary Potential on Accessories: 10/15/20% drop

Level 0-30/31-70/71+ accessories can have potential.
Permanent.

Unlimited use:

 Mercedes Link Skill: 10%/15%/20% exp

Received for leveling Mercedes to 70/120/210.
Can be linked to one character at a time; permanent.

 Pendant of the Spirit: 10/20/30% exp

Various game events. Amount increases each hour you are logged in.
Usually lasts 1 week or 1 month.

 Pipsqueak Orchid: 3% exp

Can be obtained in Monster Life.
Lasts 30 days.

 Silent Crusade Ring: 2% exp

Reward from the end of the Silent Crusade quests. Can't be obtained at the moment?
Permanent.

Limited use:

 EXP Accumulation Potion: 10% exp

Bosses drop recipe; Evo drops ingredients.

 Extreme Gold Potion: 10% exp

Drops from the boss in Monster Park Extreme at a low rate.
Lasts 30 minutes.

 Part Time Job: 30% exp

Resting job - each hour offline adds 10 minutes to the duration.
10 min * up to 6

Alternatives:
Family buff: 20% exp - Costs 900 or 2000 rep for individual version. Once per day. 15 or 30 minutes.
Family Bonding: 50% exp and drop - Requires all your Juniors logged in, lasts 30 minutes. (drop doesn't stack with Familiar buffs afaik)