Any Finesseable weapon with a higher-than-normal crit range and/or multiplier is worth considering, IMHO; although as you say, Exploit Weakness makes the crit range a little less important, but you can't take it until lvl 12. Some possibilities:
Sickle of Sypheros,
Widowblight, and
Tharkuul's Bane (Swashbuckling makes them 17-20 x3);
Threnal dagger; the dagger & dart from
RoaSP; any of the light weapons from
Co6 (particularly Sheridan's Wrack & Ruin);
GotL;
Razorend (w/SB 13-20 x3 crits + Hemorrhaging, plus it lets you delay IC:Pierce).
EDIT: there don't appear to be any named light picks, so I guess you're stuck with crafted or lootgen ones if you go that route. Too bad there's no mini-Deathnip!
