If you really want to get tricky, try combining two well-known pedals or circuits. One of my favorite pedals is the Voodoo Labs Sparkle Drive, which is basically a Tube Screamer with a clean boost circuit added. I run both together, but you can run either circuit separately as well. Distortion combined with clean boost sounds like you are runnin two amps simultaneously, and gives you scary tone for leads that cut through like a chainsaw.

A tube overdrive is a good idea, using an 12AX7 tube you'd get a really warm overdrive sound, and you basically build a small preamp.