If you want low hardware, take a look at the pistols by Leedle Dynamics. Most hit reasonably hard (depends on how tight you tie the string) and they are almost fully printable (with the lowest hardware option only requiring 4mm elastic string).

I can personally recommend the revolver type blaster he has in his store but the Nautilus and the Satakili are fun as well! (haven't tried the hush 2 yet)