Of particular interest are weapons that can be used one-handed, hidden relatively well, and are light, but I'll take a look at everything that's suggested. Weapon proficiency is not a problem for me in this since I don't intend to use it for much else besides Coup de Grace.
Right now I'm looking for things with an x4 or higher crit on their own, or anything I can make Mercurial for an x4 or higher crit. Heck, if anyone finds a long, straight blade with d6 or higher dmg and an x4 crit that I can make mercurial for an x6 I'd love you forever.
While my GM has for the most part banned Dragon Magazine material, mention it as well if you know something good from it because I might be able to convince him for a single weapon.
3.0 and 3.5 material is allowed by the way.
PS/Bonus Points: A buddy of mine mentioned seeing a one-handed scythe somewhere, what are the stats on that? Is it an x4 crit? I can't seem to find it anywhere and he forgot where he saw it.