There is a low level spell called Know the Enemy which grants +10 bonus to knowledge checks against a creature you encountered in the last day. Does casting this allow you to make a new knowledge check, regardless of number of times you have made a check?
The spell know the enemy enables Knowledge skill check retries
The complete description of the know the enemy spell says, "You commune with the divine, reflecting on one type of creature you encountered in the last day. You may make a Knowledge check regarding that creature type with a +10 insight bonus."
While the skill Knowledge has the entry Retry? No. The check represents what you know, and thinking about a topic a second time doesn’t let you know something that you never learned in the first place, that's the general rule, and the spell know the enemy specifically allows making another check—with a bonus even!—upon the spell's completion. Nonetheless, untrained Knowledge skill checks have a cap of DC 10, so even with the spell and its bonus if the caster has 0 ranks in the Knowledge skill needed to identify the creature the maximum result he can get is 10, no matter what the result would be otherwise.
However, because of its niche use and long casting time, this player's characters would be unlikely to prepare normally the know the enemy spell. It's a useless spell in combat due to its casting time, and it's a useless spell after a typical encounter with a one-off monster. (In this player's experience, because of the truly massive number of monsters available for the game, many Pathfinder encounters are with monsters that the character will never see again.) With that in mind, though, this player can imagine a wand of know the enemy being a worthwhile 750-gp investment in a long-running campaign that sees frequent use of recurring monsters.