As for climbing, don't forget the double-fisherman's... To tie two ropes together for a double-rope rappel. It's the knot equivalent of a wrist-handshake.
You should use an EDK (despite the name sounding scary) if you're anywhere with cracks or areas that a double fisherman's will get caught. The EDK is asymmetric so it's less likely to get stuck, and is generally faster to tie (and untie). Fears of it rolling out are a bit overstated - just leave a solid 6 inches of tail or more.
Or just use the Alpine Butterfly. Stronger, easy to tie, optionally asymmetric, usable as a loop or a bend, quite secure (slightly less so than Ashley's #1452 but still quite good), and non-jamming (unlike the figure 8).
I disagree that it's easier to tie, especially if you're rappelling at night. The EDK is dead simple, it's literally an overhand knot on two ropes. You can do it with your eyes closed. It's also the easiest knot to quickly inspect for correctness by your climbing partner.