•Bucket, pail: bucket is the general-purpose word. Pails are children's buckets, used to carry toys and such. Pail would never be used of, say, a miner's bucket.
•Cackle, chuckle, giggle, laugh, snicker: laugh is the general-purpose word. Giggle and snicker both mean stifled laughter with shallow breaths at immature humor (slapstick, toilet humor, etc), although giggle is the verb of choice when the subject is "schoolgirls". Chuckle is like giggle and snicker, but at something wholesomely funny. Cackling is laughing in order to send the message that you find something funny.
•Creepy, eerie, scary, freaky: scary makes you say "aaah" by invoking danger, whether real or not. Creepy makes you nervous by implying potential scariness. Eerie makes you uneasy and is more ambient than creepy. Freaky invokes not fear of harm, but of the unusual.
•Trivia, fact, factoid, tidbit: a fact is a true statement. A factoid is a fact given to be interesting. Trivia is factoids collectively. Tidbit is like factoid, but emphasizes its countability
•Gun, arm, firearm: gun is the usual term. Firearm is supposedly either broader or narrower than gun, but I can't name any non-gun firearms or non-firearm guns (gun can include cannons, but that's really more a separate meaning. You wouldn't call someone with a cannon a gun-owner the way you would someone with a rifle or handgun), so unless you can prove otherwise, firearm is just a formal word for gun. Arm can be used to refer to any weapon, but generally it just means gun. My recommendation is to just say gun.
•Tattletale, loudmouth, whistleblower: a tattletale tells of mischief of which they are not the victim to someone who might punish the offenders. A loudmouth is an insider who fails to maintain secrecy. A whistleblower is an insider who tells whoever might best get the word around.
•Shh, shush, shut up, ahem, silence, shut your piehole, hush: shh tells people to stop talking so loud. Shush specifies that it is the thing being said that should not be so loud, especially in order to not have others hear the information. Shut up is an instruction to stop talking altogether for whatever reason. Ahem is shut up with the desired goal being silence in which important speech can be heard. Silence is similar to ahem, with the implication that what is being said is merely noise. Shut your piehole says to stop talking because one is tired of processing the large volume of words being said. Hush is like silence, but with the added instruction to also stop thinking.