Examples:
I only have one Arctic Cheetah, so I nicknamed it the Cheater.
I have an Ice Fridge (you can guess which mech it is, right?)
SplatDog and SplatWolf
Scrubcrow and Skillcrow (Laser vom and streaks, respectively)
Dire Cow and a Diet Cow to celebrate their rescale
Mobile Home (Warhawk)
Then I've got stuff I personally like
Cicada X5 "Butt Burglar"
Dragon 5N "Snazzy" (my first mech ever, with the original fit I settled on; not meta but not bad either

Marauder 5M "Mr. Melter"
Marauder 3R "Phoenix Down"
Stalker 5M "Angry Grandpa" (slow, cranky, fat, but will whack you with his SRM crutches)
And of course
Kit Fox-Prime(I) "Sh*t Fox"