Gameplay:

Power-up System		"Differnet types of power-up's for example extra health/shield/minigun/weapons/speedboost/invulnerability"
Enemies		"More types of enemies also boss fights"
Damage-system		"Changing the damage amount according to the impact changment of the horse and/or the spears (for example: if the spear hits the player's leg it's damage it's smaller that when it hit's it's head)"
Multiplayer		"Co-op and versus mode added to the game also online and couch mode to play the game together with others"
Map-system		"Different types and size of playing fields also a mode to make custom ones inside the game"

Sound:

Sound effects		"More types of sound effects"
Music		"Changable background music"

Graphics:

Animations		"Better animations"
Characters		"More and prettier enemies also changable characters"

Soon:

LeaderBoard		"An in-game online leaderboard system to see who is the true western-hero"
Menu System		"An in-game menu-system for handling additional feutares and settings"

Please vote what would you prefer to see earlier happening under the "Soon" features!