1) Pogo stick
Well known from Commander Keen series, I've made it for ZDoom (original post here). It's not perfect, as it jumps higher anytime you hold the jump button, instead of jumping higher only the first time the jump button is pressed. Summon PogoStick, pick it up and have fun.
2) Power shield
A cell-powered armor that consumes 100% of the damage. Summon PowerShield, toggle it on/off by using it, but don't forget to get some cells first.
3) Commander Keen world map
A recreation of the Commander Keen world. You can walk around and do stuff (but you have to script it first ). Sprites by NMN.
Spoiler: ScreenshotYou can use these where you want, but don't forget to credit me .