Appendages (arms) – The character has extra arms. Having multiple arms is just on the border of being more freakish than a superpower.
Barbarus (Marvel) has four arms.
Elaborate Lad (Image) is an homage to the Silver Age Jimmy Olsen transformations. In Supreme V2 #45, Elaborate Lad is proof that appendages often cross the line from superpower to just being freakish.
A race of four armed aliens appears in Marvel Tales 134 #2.
Spider-Man has multiple arms temporarily (Amazing Spider-Man, v1, 100-102, The Six Arms Saga) and has trouble handling both the appearance and coordination aspects of his new “superpower”.
Spiral (Marvel) has six arms!
Mystique #5 (Marvel), Mystique (Marvel) takes on a multi armed form.
A one-shot multi-armed mutant in Mystique #17 (Marvel).
Mystique creates an extra arm in a fight with Fantomex in Mystique #20 (Marvel).
Kray-Tor (Marvel) has four arms and first appears in Strange Tales V1 #180.
In Mystic V2 #35 (Atlas), the cure for itching is more arms!
Armstrong is a character with six arms in the Savage Dragon Universe.
Why should humans have all the extra arm fun? The Octi-Ape (DC) appears in Blackhawk V1 #152.
Sheev uses his extra arms to play a deadly form of dodgeball in Strange Sports Stories #1 (Vertigo).
Space Ghost fights a four armed alien named Cutter in Space Ghost GN (DC).
Rip Roar (DC) is a demi god with four arms in Spyboy & Young Justice #1.
Ner-Nee-Nah has a lot of arms and appears in S is for Spanko: A Frightening and Realistic Giant Monster Alphabet Book (Slave Labor Graphics).
The Simbi (Marvel) are a four armed race that first appears in Black Panther V6 #13.
Meico is a four armed alien in Alien Legion: On the Edge (Titan).
Dungeons and Dragons has many multi-armed character types including Blood Fiend (D&D 4th Edition – Monster Manual 1), Chitine (D&D 4th Edition – Monster Manual 3), Girallon (D&D 4th Edition – Monster Manual 3), and Weaver (D&D 4th Edition – Monster Manual 3).
The Shi’ar Imperial Guard has the four armed Monstra (Marvel).
Arex – Who’s Who in Star Trek #1 (1987)
Athach – D&D 3.5 – Monster Manual I
Baboon – Black Panther V4 #8 (2005)
Blood Reaper – Creature Collection II. Dark Menagerie
Chitine – TSR 2145 Monstrous Compendium Annual Volume 1
Geriviar – D&D 3.5 – Monster Manual III
Gnor – Field Guide to Creatures of the Dreamlands
Gorilla – Tales to Astonish V1 #41
Marilith – TSR 2140A Monstrous Manual
Mari – TSR 2158 Monstrous Compendium Annual Volume 2
Mephisto – Silver Surfer #7 (2016)
Odopi – D&D 3.5 – Monster Manual III
Pacifiers – Creature Collection III. Savage Bestiary
Shrieking Terror – D&D 3.5 – Monster Manual III
Squealer – TSR 2158 Monstrous Compendium Annual Volume 2
The Spider – Plastic Man V2 #2 (1967)
Superman (DC) versus Briareus in Action Comics V1 #320.
Aliens with six arms want our water in Space Adventures #46 (Charlton).
Mecha Shiva appears in the Venture Bros episode Booby Traps.
Paw Pooch (DC) shows of his multiple paws in Superboy V1 #131.
The Squid does a one-shot appearance in Astounding Villain House (Dark Horse).
Some sort of six armed monster in The Books of Magic V1 (Vertigo).