I like to nickname all my Pokemon; the only exception is when I'm breeding and stopping to nickname things wastes precious O-Power juice.
Blaziken: Tends to get named after spicy chicken dishes (because fire type + chicken + kicks you in the face, soooo creative amirite?) I've had General Tso, Kung Pao, and a Talonflame named Hot Wings.
Venusaur: Basil, both a boy's name and a plant! Also had a Meganium named Dill, for the same reasons.
Gengar: Bred one for a friend and named him Moffat, after Steven Moffat, executive producer for BBC's Sherlock and Dr. Who. Because Moffat, much like a Mega Gengar, sucks you in, won't let you escape, and crushes your dreams.
Noivern: I've got a male named Gotham (bcuz Batman) and a female named Banshee (lady ghost what kills people by screaming at them = Boomburst). Also Masuda'd a shiny and named him Jackpot for obvious reasons.
Scolipede: Bred a bunch to get a good one with Speed Boost, and wound up with two boys and a shiny girl. The boys are Zerg Rush and Dexter; Zerg Rush is a Starcraft reference, while Dexter is kind of a nerdy name, and bug collecting is sort of a nerdy habit, plus sort of a DnD reference because high "Dexter"-ity = high speed and agility. The girl is Nyoom, because it is the sound speedy things make.
Swampert: Skipper, a term for a ship's captain. A nautical name for a water-type seemed appropriate, plus "Skipper the Mudkip" is super-adorable and rolls of the tongue nicely.
Espeon: I had one in my HG nuzlocke named Chuck, short for Charles, as in Charles Xavier/Professor X of X-Men. Chuck died thanks to my rival's Sneasel using Pursuit. Still sad about it tbh.
Golurk: Boltzmann, after the Austrian physicist Ludwig Boltzmann. Also, kinda has a Frankenstein-y feel to it (Bolts + Man = Frankenstein's monster had bolts in his neck), which seemed cool for a golem-like creature.
Arcanine: Giant fluffy murder puppy? All right, Cujo it is.
I also did an X playthrough where everything was a Pacific Rim reference, and a Ruby nuzlocke where every single Pokemon was named after food.
--BONUS ROUND: Nicknames I am not proud of--
Nicknaming Pokemon with basically shortened versions of their species name: Thirteen-year-old me was not a clever kid. I had a Rayquaza named Raiyo and a Charizard named Char. Let that sink in: my 13yo self thought that naming my Charmander "Char" was a cool and clever thing to do.
Sickeningly obvious/cliche names: Like a Mightyena named Fang and a Houndoom named Diablo. Or a Galvantula named Sparky and a Raichu named Yellow. Yeah, it's cute, but not brag-worthy.
Meme names: Shoop the Wooper, now a Quagsire with Hyper Beam.