3 health is a lot harder to kill with AoE than 2 health, the clone comes up before the end of turn, and the beast tag is important for some decks that might want to run it. Not all of them are worth playing, but here's a list of cards that have an obvious, useful interaction with Pantry Spider:
Houndmaster
Kill Command
Ram Wrangler
Timber Wolf
Bestial Wrath
Glaivezooka
Scavenging Hyena
Animal Companion
Infest
Stablemaster
King of Beasts
Starving Buzzard
Tundra Rhino
Call of the Wild
Mark of Y'Shaarj
Addled Grizzly
Soul of the Forest
Savage Roar
Wisps of the Old Gods
Polymorph: Boar
Dragon's Breath
Avenge
Competitive Spirit
Coghammer
Blessing of Kings
Bolvar
Solemn Vigil
Confuse
Circle of Healing
Northshire Cleric
Power Word: Shield
Holy Champion
Hooded Acolyte
Cold Blood
Tinker's Sharpsword Oil
Evolve
Primal Fusion
Rockbiter Weapon
Master of Evolution
Power Overwhelming
Darkshire Councilman
Void Terror
Usher of Souls
Inner Rage
Blood to Ichor
Whirlwind
Armorsmith
Battle Rage
Cruel Taskmaster
Slam
Sparring Partner
Frothing Berserker
Ravaging Ghoul
Death's Bite
Brawl
Crush
Abusive Sergeant
Clockwork Gnome
Voodoo Doctor
Zealous Initiate
Dire Wolf Alpha
Recombobulator
Sunfury Protector
Brann Bronzebeard
Flesheating Ghoul
Raid Leader
Shattered Sun Cleric
Tinkmaster Overspark
Spawn of N'Zoth
Cult Master
Enhance-o Mechano
Gormok
Mukla's Champion
Stormwind Champion
Rafaam
Sea Giant
Zoobot
Menagerie Magician
Curator
Defender of Argus
Knife Juggler.