Long ago, Gnomes discovered what they call Joke Magic (PDF): spells that use so little magic that they can be fueled by ambient magic, leftover wisps of spells just floating about. Gnomish philosophers believe that these joke spells actually are powered by humor itself, and that the funnier the situation, the more powerful the effect will be. Powerful wizards and mages pale at the thought, of course; magic is serious business, and must be performed with complex rituals and absolutely no laughter at all.
Neither Gnomes nor Wizards are entirely correct. As discussed previously, magic as cast by a cleric is doled out by their deity, while magic cast by a mage is stored within, and recharged by reading their spellbooks. These spells are a bit different; they take so little magical potential that they can be powered by the ambient magic of the world, leftover wisps of past spells, funny or not; in the case of these spells, the magic within the pages of the spellbooks is easily enough.
For the purpose of casting, research, and enscribing scrolls, these spells are arcane spells. However, they can be written in any language, without the arcane style of mages, and thus are able to be read and cast by anyone: arcane, clerical, or the profoundly ungifted. Other studious magic types may be able to create their own 0th level spells.
Enchanting items or creating scrolls is much simpler with these low-level spells. Characters are able to create equivalent magical items at half the level (rounded up) that they would usually be able to. For instance, a mage can scribe scrolls at level 5; however, the same mage could scribe a scroll of 0th level magic at level 3. For the purpose of finding cost and time, these spells are considered to be 1/2 level. Thus, to create a single-use effect (a scroll), it costs 500gp x 1/2, or 250gp, and it takes 1 week x 1/2, or 4 days. A permanent effect with unlimited use costs 500gp x 1/2 x 50 = 12500gp, and takes 100 days x 1/2 = 50 days to create. However, magical items using 0th level spells use so very little magic that not only is it impossible to get a better result than intended, but there is no way to improve the roll through components or better libraries.
Below are many of the 0th level spells discovered throughout the ages:
Dark flames encircle the caster; immediately and each round thereafter, without even concentrating, the caster may make an attack throw against up to 1 HD per caster level of creatures within 60', lowest HD creatures first, doing 1d4 damage to each. Creatures with 8 or more HD cannot be targeted. A saving throw against death avoids damage. The effect lasts for 1 round per caster level.
The caster targets up to 4d8 creatures within 60', least HD creatures first (creatures of 8 HD or more cannot be targeted). On a successful attack throw, each creature takes 1d4 damage, unless they make a saving throw vs death.
The caster targets all creatures in a line 60' long and 5' wide, beginning at his fingertips; on a successful attack throw, each creature takes 1d6 damage. A saving throw reduces the damage by half.
on a successful attack throw, the caster causes 1 creature within 15' to take 1d6 damage every turn, until it saves vs. blast, or the caster stops concentrating.
On a successful attack throw, the caster causes 1 creature at melee range to take 3d4 damage; a save vs blast will avoid the spell effect.
The instant the spell is cast, the caster is enveloped in a 10' diameter sphere of flame; anyone caught in the flames, including the caster, is burned for 1d4 damage (this is a trap spell).
The caster causes a pile of kindling to appear at his fingertips in an area up to 10' cubed, but bonded to the ground, immovable. The size of the pile is chosen by the caster at the time of casting. A magical fire consumes the bracken, blocking vision, but not light. The kindling lasts 1 turn; when it is burned up, it vanishes entirely. It is affected as wood by physical and magical effects, though any creature that attempts to cross the flame will be hit with 1d6 magical damage; a save vs blast will limit the damage to half.
The caster summons an invisible wall at his fingertips, up to 1" thick, 10' wide and 10' tall. The wall is impermeable to magic; any magical effects used against it or through it will dissipate harmlessly. Physical effects, however, go straight through the wall; weapons, including arrows, are entirely unaffected, as are creatures, unless they are entirely magical. The wall is bonded in place, and must always be a flat, vertical plane. It lasts 1 turn.
The caster targets up to 1d4 living humanoids at melee range, lowest HD first. Each one he succeeds his attack throw against falls into a magical sleep for 1 turn per caster level. Creatures with INT greater than 12 may save vs spells to avoid the effect.
On a successful attack throw per animal, the caster causes up to 1d4 living animals of any HD within 15', fewest HD are first, to become confused. Intellegent animals may save vs spells to avoid the effect; otherwise, the spell lasts 1 round per caster level.
The caster targets up to 1d4 living humanoids of up to 4 HD, at melee range, fewest HD first. On a successful attack throw per creature, the creatures become charmed for as long as the caster remains stationary and concentrates. A saving throw avoids spell effect.
The caster sets an alarm, to be triggered in any way he sees fit, as long as it only uses sight and sound. Anyone within 30' of the alarm will trigger it unless they save vs spells. Once triggered, the alarm makes a loud sound (of the caster's choice) on a 10-second-loop, for a full turn.
The caster touches one creature; that creature suddenly begins hearing a loud cacophony of unrecognizable sound, masking any other noises. The sound continues forever, until the target saves vs spells.
The caster causes one creature within 30' to see a pre-recorded loop of the landscape in front of him. If the target moves, speaks, casts a spell, attacks or is attacked, or even touches the landscape, the illusion will vanish; otherwise, it lasts as long as the caster concentrates, plus 4 rounds.
The caster targets one creature within 60'; as long as that creature does not move or attack, the caster can speak to the target. Only the target will hear the voice. The effect lasts as long as the caster concentrates.
Upon casting this spell, the caster (and the caster alone) will hear several echos of his own thoughts or words, which causes him to stutter for the next turn, or until he successfully attacks or is attacked. This has the effect of making him unable to cast any spells; to successfully communicate, he can only speak two words per round. (this is a trap spell)
Once this spell is cast, for as long as the caster concentrates and does not cast a spell or attack (even by methods that do not break concentration), the caster is entirely immune to fear, and any spells or other effects relying on sight, sound, touch, taste, or smell; the caster is transported to his happy place. He can move as normal, but will not interact with (or notice) anything around himself.
The caster summons a number of goblins, totaling his own level, within 10'. Each goblin may make a save vs spells to refuse. Each goblin must be given a task; upon completion of the task, the goblin will be freed and vanish. However, the goblins are actively hostile to the caster; if the caster ever stops concentrating, the goblins will immediately attack him. Regardless, the goblins will vanish after 6 turns.
The caster summons a Nyad; the creature remains until dismissed by the caster, having performed a task, or a full turn, whichever is first. The nyad is actively hostile to the caster, who must concentrate to control her. If the caster loses concentration, the nyad will immediately attack, and can no longer be dismissed early. However, nyads can cast water breathing, which is a useful task. The spell takes one turn to cast.
Faerie's make excellent spies, as they can turn invisible at will, and attack without losing their invisibility. The summoned faerie remains until dismissed by the caster, having performed a task, or a full turn, whichever is first. The faerie is actively hostile to the caster, who must concentrate to control it. If the caster loses concentration, the faerie will immediately attack, and can no longer be dismissed early. The spell takes one turn to cast.
Summon Green Slime
The caster summons a green slime within 10'. He may give the slime a single task; once that task is completed, or after 1 turn, whichever is first, the slime will vanish. However, if it has reproduced, those slimes will remain, though they cannot be controlled by the caster. The slime will not harm the caster or his allies as long as the caster concentrates; if the caster loses concentration, the slime will try to attack him.