Mill Creek from Ponderosa Rd. Since its season is later than Deer Creek's, it is possible to do both runs every year. Although the water is quite silty because of volcanic ash deposits high on Mount Lassen, the lava scenery is fantastic. In perhaps a dozen places, the creek runs thru deep gorges only a few meters wide, often with ferns growing from the overhanging cliffs.
Locals claim to have jumped from one bank to another, which is certainly possible at several spots.
Class IV rapids occur consistently, until you hit the diversion dams in the Sacramento valley. Stanley's second-hand 2nd edition writeup claims that some plastic boaters did the whole run without portages. As usual, the truth is probably somewhere in the middle. Dead Man's Narrows, a log-choked class VI nightmare around mile 23. However Holbek's 3rd edition writeup gives the impression that he ran this in 1993.