Practically, Travel Light and Toughness are useful perks if you don't intend to switch into armor and stick to your light mechanic's clothes. If you're a VATS sort of guy, Gunslinger or Sniper aren't bad choices (the latter only useful for headshots, though). Cowboy is handy if you intend to stick to revolvers, but mind the 45 Melee requirement. Finally, if you intend to drink a lot, Chem Resistant and Chemist never hurt.
For hilarity, though, find a Raider arclight helmet and wear it with some suitably greasy overalls (such as the Handyman Jumpsuit), so as to pass for a heavy-duty mechanic. Imagine your Courier somehow getting roaring drunk under a welding mask and talking to everyone through it.
My current humor build revolves around an Asian Courier piling as many points and perks into unarmed/melee and durability as possible, alongside some decent heavy leather armor and specifically the Bloody Mess and Implant GRX perks. I punch people at hyper speed until they explode.