Stats
 

I have a level 30 cleric, and I want to raise his weapon skill. What is the minimum level mob I can fight and get weapon skills?

Something that gives XP, i.e. 2/3 of your level. Level 20+.

May I suggest this guy:

http://wiki.project1999.com/Slaythe

A triggerable level 20 froglok rogue in Misty Thicket, with no meaningful faction hits.