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"