This is your opinion, so feel free to say what you like as longs as its not insulting or irrelevant.
To me these are banknotes which are universally dirt common, very cheap, have almost no collectibility and you see them anywhere.
Examples - Inflation notes, ultra low values, cheap and nasty looking notes.
Choices must be legitimate circulating currency banknotes, no propaganda or funny money ones like political satire notes, university capping money or fake money from micronations like Hutt River.
Mine are
1. All German Inflation notes issued between 1921 and 1923 - all worthless and seen in quantity - most are poor condition.
2. Yugoslavian inflation notes from the 1990s and early 2000s - recycling old designs over and over. Serbia Yugoslavian ones from as late as 1998 still showed Tito!
3. Those Indonesian Satu sen notes of 1964 - the ones from 1 sen showing a peon to 50 sen showing a soldier - cheap children's rubbish and more a gimmick issue that saw little actual use.
4. The Brazilian and Peruvian inflation notes of the 1980s - you know the 10000 Cruzados nova and 1000 Intis with the Inca etc. Printed into the kajerillions and stockpiled when rampant inflation meant none ever got issued and instantly sold to packet makers.
5. Ex soviet stans currency of the 1991 - 1993 era, all those rublenickis, rubleys and noworthniks notes, you know like that square note with the bird on it, the first Belarussian series from 50 Kapek to 100000 Rubley and you always see the 50 Kapeky or the 1 Rubala. They all look cheap and awful and are completely worthless junk.
6. Zimbabwe 2000s - why people are paying $100+ for the 100 trillion note is bizarre, apart from having lots of zeros on it, it has no practical use. Same with all the other notes that recycled 5 or 6 designs on values from 1 cent to trillions of dollars.