Serious Sam: The Second Encounter

Serious Sam: The Second Encounter is Serious Sam: The First Encounter's sexier younger sister that everyone loves over the older sister. It's got new enemy types, more challenging enemy layouts and has better levels; how can you not love it? Unfortunately, it has very little unused content compared to its prequel.

Like TFE before it, it also has an HD Remake, but there are a few changed things, such as the rooms with physics-defying gravity being altered due to problems with the new engine. None of it really affects the game though.

The First Encounter resources
Everything from Serious Sam: The First Encounter is included in the game's files. Almost all of the Egypt textures go unused (except for a few in the Tower of Babel's TFE throwback secret) and all of the Egypt-themed keys are unused as well.

TFE Unused Enemies and Weapons
The resources and coding from the unused enemies and weapons that appeared in TFE's files are in the game as well, but some of it is used (such as the South American boss using the coding for the Air Elemental's whirlwinds) or the concepts are resurrected (such as the Flamethrower/Flamer).