Bowline, with the variation of bowline on a bight. Non slip knot, can be used to raise/lower a person.

Clove hitch, used for tying things up, as in bundles, a tent line to a tree. Variation is clove hitch with quick release.

Square knot, used to join two like ropes together.

Taut line hitch, used on tents as you can release or add tension w/o retying the knot.

Overhand knot. The most simple.

I'd call these the big 5.