A few adjustments from a rock climber and camper here:

1. When joining identical ropes, the reef knot is adequate for any situation where the sheet bend is adequate. The rolling over and jamming under load described above usually happens when joining different ropes. Deconstructed, the sheet bend consists of a loop in one rope and a bight in the other: you want the loop to be in the 1) thinner or 2) higher-friction of the two cords (in that order of priority). There doesn't seem to be any downside to using the sheet bend over the reef knot in identical ropes (besides perhaps complexity) so I tend to agree with the implication above that the sheet bend is the superior knot. Neither knot is recommended for life support applications.

2. The bowline coming undone under non-continuous load is very real and has resulted in some climber deaths. However, I think the half hitch addition suffers from the same issue--it merely takes longer to come undone this way. A more reliable finishing method is to tie a double overhand in the tail either around the loop (see [1]) or around the standing end (this is common and effective but not my preference for purely aesthetic reasons). The double overhand binds under load, but load will be intercepted by the bowline's turn and the overhand should never come under load. A double bowline will extend the life of your rope by widening the bend that comes under pressure, but isn't appreciably safer in adequately strong ropes.

3. The clove hitch coming undone under non-continuous load doesn't seem to happen as much with flexible ropes (such as those used in climbing) but nevertheless climbers typically use this knot when the entire standing end is between them and the knot coming undone. As with the bowline I'm skeptical that half hitches fix the problem with loosening--if you're hitching near the end, rather than adding half hitches as recommended above, I'd use an anchor hitch or buntline hitch--both of these are adequate for life support (OSHA approved for rope access work, frequently used by arborists).

4. For climbing, at least in the US, the figure-8 retrace is far more common than the bowline as an end loop knot. The upside here is that it's easier to verify the knot. The downside is that the knot is harder to untie (there are some variations that are easier to untie than others[2], but all variations bind more than a bowline).

5. You'll notice that in 1, I haven't mentioned a knot for joining two ropes that's appropriate for life support. The flat overhand is used by climbers for rappelling, but is known to roll under higher loads--standard is 12 inches of tail and I personally always back up with a second flat overhand of opposite chirality (the loop is in the opposite direction, so if the knots both roll, they have to roll against each other). Under greater load or non-continuous load, I would use an alpine butterfly with a flat overhand backup: similar to the bowline and double overhand, the finishing knot binds under load but shouldn't come under load. If you never intend to un-join the ropes, the double fisherman's bend is probably safest, but binds extremely tight under load.

6. Trucker hitch is very useful for tying down loads or removing slack from systems (I use this for tying down tents or tarps when it's windy, or tying loads on trucks). There are many variations, but the key components are a midline loop, the rope going to some attachment and then "pulleying" through the midline loop, and then a knot to fix the end. The simplest would be to use a slipknot for the midline loop and two half-hitches to fix the end--this is adequate because the tension keeps the knots under constant load. However, if you want to remember fewer knots you can use some of the knots from above: overhand on a bight and clove hitch or anchor hitch will work just as well though they're a bit slower to tie.

7. A friction hitch is useful: the Prusik is simple and doesn't have any directionality worries.

To summarize:

1. End loops: bowline with a double overhand on the loop (easier to untie) or figure 8 retrace (easier to verify).

2. Joining two ropes: sheet bend (not for life support), flat overhand (short-term/low-force life support), alpine butterfly with flat overhand back up (long-term/high-force life support), double fishermans (never untie, ever).

3. Tying to a pole or carabiner: clove hitch (middle of rope) or anchor hitch (end of rope).

4. Tying down loads, removing slack: trucker hitch.

5. Frictioning one rope against another: Prusik.

[1] http://www.animatedknots.com/images/bowline_stopped_in_loop....

[2] https://www.youtube.com/watch?v=QAr-uHd8h8o