Looking at how many fingers I have has been pretty successful for me. Once, I was sure I was awake, but just wanted to get in the habit of doing that reality check so I looked down at my fingers. I had fleshy lobster claw fingers. Basically a lobster claw on each hand, two fingers per hand. It made me laugh, and I got a lucid dream out of the deal.

What about facing your worst fears? I fear being attacked by some being of vastly superior strength, weaponry, and skill, or in whatever way that I have no chance of survival. I've been purposely trying to summon such a beast as a reality check today. If such a beast appears, I must be dreaming, and therefore, I can defeat it with lucid dream abilities. Or just become invincible and ask it why I am afraid, then move on with lucid dream goals.

I like the levitation / flying reality check. That one is fun to do.

In my experience, whatever you really expect to happen in a dream is what happens. So if you can make yourself really expect something (maybe something amazing instead of scary) and it happens, that could be fun too.