I'm one of the few people that actually carries jumper cables on my bike (in the trunk). Mostly, other people end up borrowing them, but I like being prepared...
I found a pretty cool small tool kit at Home Depot, which I stick in with a few other tools in an emergency kit I found at walmart (JustinCase, had the jumper cables, can of fix a flat, flashlight, zip ties, cloth gloves, couple of gauzes/band aids, and some other stuff). I also added a 3/8" longer ratchet, a long flat head screwdriver, a pair of needle nose vise grips (these come in handy if you mostly break off a cluth lever like I did earlier this year), tiny can of WD-40, a spare headlight bulb, a couple of larger sockets (still need to get the one for the wheels though), and I just happened to have a spark plug socket that works well with Connie plugs (although I still have the OEM socket under the seat). I also have a few box/open end metric wrenches (and an extra, longer 10mm for the valves). It's a tight fit, but everything fits in the Justin Case.
http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&productId=202342064&langId=-1&catalogId=10053&ci_sku=202342064&ci_kw={keyword}&cm_mmc=shopping-_-googleads-_-25-_-202342064&ci_gpa=pla&locStoreNum=4403The small tool kit has SAE and Metric sockets. I considered just packing the metrics, but figured ya never know when a Harley guy might need assistance... It is similar to the one below (stubby ratchet and screwdriver), but has more sockets. I use the #3 bit a lot to remove the fairings and such.
http://www.kaboodle.com/reviews/husky-40pc-mini-stubby-setAlso, the Justin Case has a fold out pocket that I put a partially used roll of gaff tape, brake fluid, homemade funnel (sits on top of the brake fluid bottle/gaff tape), glass cleaner, and a larger bottle of water (for me or the bike). I also have a small compressor (with tire plugs) in a separate case, as well as a small first aid kit. Plus, I have a small electrical butt connector kit (crimp tool plus assortment of connectors) inside the Justin Case. I also carry a short length of electrical wire and 12" of 1/4"(?) plastic tubing for brake bleeding and float bowl draining. I also have a regular pair of needlenose pliers. I also have a very nice assortment of Allen Wrenches wedged next to my Justin Case. I also have a Seafoam can that I have some Rotella T Synthetic in (I taped the can up and wrote 5w40 Oil with a silver sharpie). Needless to say, with the bungees, terry cloths and cargo straps I also carry, my trunk is quite full...
The Justin Case will fit into a sidebag with room to spare. Possibly with the fold out pocket open. But since I leave the trunk on the bike all the time, I put the kit in the trunk.
Finally, I have a 130mm x 8(?) mm bolt to use as an emergency peg should I break a footpeg (which I am currently using as my footpeg).
While you don't need to go to this extreme, I'd at least very much recommend the needlenose vise grips (which were recommended to me here, which is why I bought them) as part of your tool collection. Also, a small assortment of butt connectors and a short length of wire won't take too much space, should you ever need them (you can always use regular pliers to crimp the connectors in a pinch). Plus a fuse assortment of course.