Always carry a full set you never know when it might come in handy, and 99.99% of the time I'm pulling them out of the trunk to fix someone elses car, and as life has had it so far the only time I have ever had a problem is when I left the tool box at home.

I carry
-Craftsman 204 piece tool set
-Gearwrench wrenches (Full metric Set)
-Balljoint Fork
-Voltmeter
-Soldering supplies
-and some other misc. whatever I throw in my tool bag
-GM Performance Low Down Jack (< Wal-Mart Special Works Great for Hondas)
-And the usual full spare (An extra 15x6.5 with a brand spanking new tire)
-Spare WBO2 sensor in case mine goes bad away from home.