About chill touch:
I think that chill touch has actually, under very special and rare circumstances some use. It is a weapon spell that creates an item in your weapon slots, which does very minor damage. But this item is at the same time unenchanted AND does elemental (cold) damage. So it can pierce at the same time protection of magic weapons and stoneskin. The only other weapons that are capable of this trick are the crossbow of searing, the firetooth crossbow and gesen's bow, all of which are missile weapons, loaded with unenchanted ammunition. Chill touch remains as the only melee weapon that can pull this stunt.
User Unfriendly writes in his cheese guide
(link) about killing Kuroisan with the crossbow of searing and unenchanted ammo punching simultaneously through PfmW and Stoneskin (If you want a detailed explanation of the process read the Cheese Guide). Since Kensai->Mages cannot use missile weapons they have to rely on chilltouch in this case if they want to make use of this weakness. Apart from that, this would be the only possibility for pure mages/sorcerors as well, as they can't use crossbows and bows, but lacking fighting capabilities it might not be a very wise move going toe to toe with Kuroisan.
Other than that I see no use for chill touch and I'd like to qote Xyx' spell reference
(link) about this spell: Chill Touch
The worst kind of spell; useless and puts the caster in danger. You have to roll to hit, the target gets a save and even if it works this hardly does anything. Avoid like the plague.
I can only recommend the Spell Reference by Xyx. For all who wonder whether certain spells are useful or not, it may be worthwhile checking out Xyx' opinion on it.