Don't have 3.5 so my comment is 3.0 style.
Grease and Blindness/Deafness. Friend of ours was just about to start a new campaign, we had maybe done 1 session of it under 2E, when 3E came out. He rewrote the whole thing quickly to 3E and we went to town. The world was very anti magic but I was playing a wizard heh. Paladin in our group would have killed a wizard on sight but he just thought I was a bad fighter b/c I naturally didn't wear robes and such. Other guy in the group was a Thief/Cleric and the Paladin was alright with that b/c they shared the same god I think.
I learned the power of those 2 spells very quickly. We were sneaking into a camp and taking out sentries along the way. A group of them are walking the compound and I cast grease under them. They all fail their saves and fall down, having trouble standing again. I believe that our DM ruled the grease to be flammable and we used a flaming arrow to take them out.
Blindness was just a common occurrence and the Paladin (the character was VERY stupid) always thought their helmets must have fallen over their eyes or something. This was a ton of fun and I learned exactly how flexible a couple of dinky spells could be heh.
Hagen