Canon 7D body, Canon MP-E 65mm lens, and Yongnuo twin flash -YN-24EX
This is my favorite of the two setups. Its greatest limitation is the fact that I can't shoot anything larger than 2 cm. It is extremely challenging to approach bugs without spooking them, as this lens doesn't allow to shoot anything farther than 2.5 inches.
I just bought this flash system and need to keep experimenting with it, but so far I am very satisfied; especially considering its low price

I like to use these camera/lens/flash/diffuser combinations to shoot, handheld, on a white background and rarely on a black background. To stabilize the camera, I use any firm object that I can lean the lens on and then move the camera up and down to focus the image (when taking dorsal shots). The shooting surface serves me well for supporting the lens to photograph a bug from a lateral angle; then I just need to tilt the camera up or down for sharper focus.