I discovered the weekly challenges at the r/Darts subreddit recently and I think they are quite swell. They are very easily mixed in with regular practice, especially doubles practice. This week's challenge is as follows:
Easy Challenge: Checkout 60
Medium Challenge: Checkout 95
Hard Challenge: Checkout 118
The easy one was quickly gotten, although I missed the second dart. I was going for S20, D20, but missed the D20 into the single, then hit the D10 for the successful checkout.
The medium challenge took a bit longer. I spent a few rounds trying to go T19, D19, but quickly abandoned that for Bull first dart. This could go several ways: 50, 5, D20, or 25, T20, D5, but in the end, after probably a good 40 minutes of throwing I finally took it out with Single Bull, S20, Double Bull.
The hard challenge took two solid days of throwing. I started by trying for T18, thinking if I hit the S18 I could go T20, D20, but then I abandoned that for T20 first dart. I ended up with many, many rounds in which I hit the S20, T20 and missed the D19 by a wire but I never hit it during that first session of trying. The next day though I was out throwing darts with my neighbors and I finally hit it: