Open E Bassline
For this challenge, you're going to start by playing a consistent beat with your picking-hand's thumb on the low E string. Then, while you're doing that, try playing an E minor or major pentatonic scale, or part of one.
If you've never tried this before, it can be difficult, but once you get a hold of the concept it can be quite fun. If it's really difficult, first plan the scale or scale fragment to play, practice it a bit without the bassline, then try to incorporate the bassline. This one is a little more challenging than usual, but give it a shot!
Those of you who feel like you're getting the hang of it, try writing a little melody instead of playing a scale.
For those of you feeling really adventurous, try making a melody using on and off beats.