For a solo campaign, I'd go with one of the following 3 ideas:
1. Druid. As other have said, it's as close to a one man party as it gets. You can melee, are a full caster, you have an animal companion and SNA creatures make for dispsable trapfinders.
2. DMM: Persist (cloistered) cleric with kobold and travel domain. You are a full caster by default (although cleric spell list lacks in certain areas), DMM: Persist makes you a combat powerhouse at lvl 7+, and Kobold (trapfinding) and Travel (mobility) help round your character in two very important areas.
3. Chameleon. You can build this char in quite a number of ways (my favorite is cloistered cleric 1/paladin 2/fighter2/chameleon x; I think credit must go to Caelic for that), but you will most certainly be able to cope with a lot of situations due to the inherent customization of your abilities the class allows you to do daily