I'm pretty bad when it comes to give nicknames to pokémon 'cause I'm not that creative (only sometimes). But I NEVER catch a pokémon without nicknamin' it. (Even the ones I catch just to complete the pokédex) I feel strange when I have a pokémon with its original name (Especially in my party, I feel like I don't like my pokémon. :3 Yep, strange)
I usually use simple 'n fast names, nothing extraordinary. In my first time playing Platinum, I have nicknamed my turtwig "Leaf". '-' In my second time playing it after a year or so, I've nicknamed my turtwig "Leaf 2.0"(I can't choose any other, turtwig is so awesome. :3) I did the same thing with my starly, "Raptor 2.0". '-'
In GSC/HGSS, I've chosen Cyndaquil. In HGSS, It was a female, so I nicknamed it "Cinnamon" XD In GSC, It was a male, so I named him "Xplotaro", a reference to Gold's Cyndaquil/Typhlosion.