Along the same lines as Shrapnel Launcher is the Dwarven Musketeer. Questions, comments, suggestions? :D

Wizards doesn't like doing repeateable pingers at common any more. Bump this to Uncommon and maybe add an activation cost...: would make it into a walking Shock which could fit what you want to do. At common you could get away with this costing and doing 2 damage as an etb effect.

Uncommon and an activation cost? I having difficulty coming up with common cards that are still good/support/utility cards. Hmm, you don't think the 'doesn't untap' is a big enough penalty? Could I get away with it at common as is + activation cost?

could probably keep it common if dropped to 1 damage, 2 damage is too strong for common would still need activation I'd think.

Just as a data point, in the recent Second Great Designer Search, one of the multiple-choice questions was "Which of these effects might happen at common in a new set?" One of the options was a pinger (": ~ deals 1 damage to target"). It was not the correct answer.

Wizards have been making a big push to simplify commons, and yes, this does make them hard to design.

Hmm. Points taken. I'll bump it to uncommon, and throw on the activation cost. :D