All right, seriously?
- Figure 8 Follow Through (one direction for tying in to a harness, the other direction for tying a rappel knot);
- Figure 8 on a Bight (for making a loop in the rope);
- Water Knot (for tying slings);
- Clove Hitch (for tying in/equalizing an anchor without having to carry half a ton of crap on your harness);
- Munter Hitch (an alternative method to belay without a belay device);
- Prussick (for holding and/or ascending the rope);
- Euro-death Knot (which I use exclusively for rappelling at Red Rocks; it's the best rappel knot for not getting stuck/jammed, and Red Rocks has so much stuff sticking out just waiting to catch a rope).