One tool I'm very fond of is the Park MT-1 "dogbone" type multi-tool. It's about 4" long, weighs 50 grams and costs under $10.
The MT-1 has 3,4,5,6 and 8mm hex keys, 8,9 and 10 mm box wrenches and a small flat blade screwdriver, The best thing about its design is that the larger hexes, 4-8mm, are at the ends of the tool and at right angles to its length so you can get real leverage if needed. I once used the 8 mm hex to reinstall another riders crank that had come loose. Try that with your Alien.
I also carry Richey's tiny 25 gram chain tool (CP-5?). The combination of these two tools does almost everything the massive multi-tools do at a quarter the weight and half the cost and bulk.
Finally, the question as to which tool do you use. You are not a carpenter, you don't expect to use your tools, but you better have them just in case. I rarely have had to use them on my own bikes but I've bailed out several other riders over the years.