Here are some little UE4 tech demos mainly to example how to create gameplay mechanics using Blueprint

2D Platformer



Double Jump (or more), Doors/Teleporters & Keys, Falling Blocks, Moving Platforms, 1 Way Platforms, Spikes, Collectables (with changeable values), Talking NPC's, Moving Enemies, Checkpoints, Ladders (bit clunky), Goal with end score.

Tower Defense


Towers (missile and slow), Lives, Wave spawning, Resources.