A TLR for sure (such as Rollei or Yashica) based on personal experience. Good results and people love it. Old people reminisce, young people assume credibility.
The 120 SLRs can look and sound cool. I havent' owned 120 SLRs, but I'd agree the Hasselblads look the nicest and have a pro reputation (despite the fact that pretty much all 120 SLRs were made for pros)
The folders can be pretty darn cool and take good photos too. The oldest ones look cool but can be difficult to focus for short depth of field as they have scale focusing. Something rangefinder folder can be also cool. The fuji gf670 looks modern and quaint at the same time. A shame it's so expensive. certo6 is a popular ebay seller for old and oldish folders.