How many name prefixes can be stacked onto one weapon?
Solution 1:
To start with, Strange and Killstreak can be applied to almost any weapon (of any quality). Both of which could add up to two words to the name.
The following qualities do not interact at all:
- Vintage
- Community
- Self-made
- Australium
- Festive
- Genuine
Some other qualities exist like Unusual & Haunted, but they apply mostly to cosmetics and some special weapons such as the Horseless Headless Horsemann's Headtaker.
You can add Collectors to both Festive and Vintage (not sure about the others because how rare they are).
You can also add 'Strange Filters' to items which will add an additional prefix word based on the map that you are filtering.
Example for longest weapon prefix:
Hale's Own Frosty Professional Killstreak Collectors (Festive/Vintage) WEAPON
Update: I have no idea how all of this fits in with the new 'Decorated' weapons released with the 2015 Gunmettle update.