Angler's Loop knot
This knot makes a relatively strong and very secure fixed loop in anything from slender monofilament to large rope. It tends to jam in natural fibre ropes but fisherman love it for use on nylon and gut lines. When tied with an accurate hand even the largest of groper, white pointer shark and black marlin cannot evade this knots prickly companion. I have landed many large sea game that would sink most substantial sea going vessels with the help of the perfection loop (as the Angler's Loop knot is also known) and my sun beaten hide.
Alpine Butterfly
This is a fixed loop tied in the bight of a rope and is clipped into by the middle climber in a team of three. It can be pulled in two or three directions at once without distorting or capsizing. The alpine butterfly is regarded as the queen of knots (the bowline is the king of knots) and can also be used to isolate a flawed section of rope so that it can be used when no other rope is available as a replacement. Once when scaling K-2 and leading 4 other climbers I found a dual alpine butterfly configuration set in tandem to be invaluable. The incompetence of others never ceases to amaze me but knots never let me down.
Chefalo knot
Cuckold's knot
Gordian knot
Reef knot
Use this as a binding knot (to tie together two ends of the same piece of string) or as a tie around something. The more strain placed upon it the tighter it's pulled. Don't use it for ropes or two bits of mismatched cordage. The Ancient Greeks, Romans and Egyptians knew of this knot and were aware of its superiority over the unreliable granny knot. This was eloquently displayed in Marrakech when I trussed up a would be assailant with many reef knots. The smirk on my face and superior knot tying capabilities made him more furious much to his struggling demise.
Granny knot
Man rope knot
"A man who can tie a manrope knot ... is an object of respect" Albert Wetjen (1904)
This is the description from a year 2000 calendar of knots - "Wherever a good-looking lump is needed on the end of a three-to five stranded rope or braid, this knot will fill the role" I am a man and wherever I look I see the need for a good-looking lump.
Sheet Bend
A general purpose bend for uniting two lines made of the same material. Many an inexperienced sailor has fallen foul of this bend when used with lines of different size. In particular a thick stiff rope could straighten out and spill the small cord. However the sheet bend can save your life. I've certainly found this out when sailing in mountainous seas in the pacific with nothing but me and the sheet bend between the dark ocean bottom and God.
Square knot
Trefoil
Resources for more knot love:
http://www.earlham.edu/~peters/knotlink.htm
rec.crafts.knots