Games like PigPonyPocalypse
Games like PigPonyPocalypse include Enter the Gungeon, Nuclear Throne, Bit Blaster XL, Furi, and Touhou Koumakyou: New Classic - the Embodiment of Scarlet Devil. We matched them by the tags players give PigPonyPocalypse on Steam (Boss Rush, Bullet Hell, Difficult, Twin Stick Shooter, and Action): closest matches first, and among equally close ones the better-known games.

Enter the Gungeon
Shared: Bullet Hell · Difficult · Pixel Graphics

Nuclear Throne
Shared: Difficult · Bullet Hell · Action

Bit Blaster XL
Shared: Bullet Hell · Difficult · Shoot 'Em Up

Furi
Shared: Bullet Hell · Boss Rush · Difficult

Touhou Koumakyou: New Classic - the Embodiment of Scarlet Devil
Shared: Bullet Hell · Difficult · Shoot 'Em Up

Chippy
Shared: Bullet Hell · Twin Stick Shooter · Difficult

Bot Vice
Shared: Bullet Hell · Difficult · Top-Down Shooter

Assault Android Cactus+
Shared: Bullet Hell · Twin Stick Shooter · Difficult

Voidigo
Shared: Twin Stick Shooter · Bullet Hell · Shoot 'Em Up

Star of Providence
Shared: Bullet Hell · Shoot 'Em Up · Difficult

Nex Machina
Shared: Bullet Hell · Twin Stick Shooter · Action

BALL x PIT
Shared: Bullet Hell · Action · Shoot 'Em Up

SYNTHETIK: Legion Rising
Shared: Action · Top-Down Shooter · Difficult

Titan Souls
Shared: Difficult · Boss Rush · Action

Dead Estate
Shared: Twin Stick Shooter · Difficult · Bullet Hell

LUFTRAUSERS
Shared: Bullet Hell · Action · Shoot 'Em Up

The Void Rains Upon Her Heart
Shared: Bullet Hell · Boss Rush · Action

Hotline Miami 2: Wrong Number
Shared: Action · Difficult · Pixel Graphics

Waves
Shared: Bullet Hell · Twin Stick Shooter · Shoot 'Em Up

Rubinite
Shared: Boss Rush · Difficult · Pixel Graphics

Relic Hunters Zero: Remix
Shared: Twin Stick Shooter · Action · Top-Down Shooter

ZeroRanger
Shared: Bullet Hell · Shoot 'Em Up · Action

Touhou Tenkuushou ~ Hidden Star in Four Seasons.
Shared: Bullet Hell · Difficult · Shoot 'Em Up

Touhou Kouryudou ~ Unconnected Marketeers.
Shared: Bullet Hell · Action · Shoot 'Em Up