Delphox: Firefox (My web browser! 
Venusaur: Blossom, Bloom, maybe even Flora once? (The bud it has as a Bulbasaur blooms into a flower.)
Aegislash: Masamune (After the sword Frog uses in Chrono Trigger.)
Swanna: Cygnia, Aquarelle (I had a hard time coming up with a nickname for it in X. I used Cygnia at first since cygnus is the name of the genus swans belong to, but Aquarelle sounds better. Coincidentally, aquarelles are a type of watercolor painting.)
Florges: Flora, Antheia (Another Pokemon I used in my X playthrough. I named it Flora originally for obvious reasons, but after I evolved it I renamed it Antheia since according to Bulbapedia, the line may be inspired by that Greek goddess.)
Flygon: Toph, Myrm (I named a female Flygon I used in Pearl after Toph from ATLA. In my X playthrough, I caught a male Trapinch and struggled to find a name for it. The line is based on antlions, and I noticed that they belonged to the family Myrmeleontidae. Wyrm is a word for dragons, so why not combine those two somehow?)
Pikachu: Zappa, Electra, and probably other horrible electric puns.
Gardevoir: Hikari (Japanese name meaning light)
Gallade: Link (from Zelda)
Metagross; Metaknight (from Kirby)
Kyogre: Sapphire (Yes, I actually did this.)
Blaziken: Phoenix (Well, it is a fiery bird...)
Empoleon: Mumble (from Happy Feet)
Charizard: Dragonfire (It was dragon like and I was playing FireRed at a time I was into Winx Club for some reason. The 4Kids dub called Bloom's power the Dragon Fire so yeah...)
Weavile: Vira (It was a female dark type and Vira sounds similar to virus.)
Weezing: Poisonwind (Um...it's poisonous and gaseous?)
Vaporeon: Ariel (Hey, it does looks kinda like a mermaid.
Lapras: Nessie, Oceania
Milotic: Baikal (After Lake Baikal in Russia.)
Stunfisk: T-urdfish (Because the censors in X would not let me name it Turdfish.)
Panpour: Cali (I was considering using it on my team in X but I scrapped it. Short for California, its evolution looks like a surfer dude to me. Do not question my logic.)
Meganium: Gaia, Gardenia (Gaia is an earth goddess and Gardenia is a flower that also contains the word garden?)
Blastoise: Leonardo (Pfft, TMNT.)
Swampert: Everglades, Skippy
Starmie: Stella, Cosmo
Gastrodon: Squishee
Staraptor: Windstar, Gale. (Flying type with the word star in its name? And well Gale is...wind...poof.)
Girafarig: Grimmer (A character from an anime called Monster. He's a tall guy and the fandom jokes about him being a giraffe.)
Infernape: Tarzan
Roserade: Rosacea (A skin disease that coincidentally sounds like it's a flower related to roses...)
Pidgeot: Superwing, Bobo (Superwing was my beloved overleveled Pidgeot from Yellow. In a playthrough of Fire Red, I used a Pidgeot named Bobo because of an in-joke my cousin and I have about a bad translation of Pokemon Green.)
...And that's just off the top of my head. As you can imagine, I love nicknaming Pokemon. ^_^
ncG1vNJzZmiapaGvorPAq5uepl6jsrV706GpnpmUqHykuMSvnKtloKS4prnOp2SnoZOgu6K5xKxla2xgaoNwvMCgnGZwYQ%3D%3D