An RDV4… but that doesn’t mean I like it.
Purely a means to an end.
I would prefer to have something small and “robust” I can just throw in my bag,
pull out,
read - write - done
There are125kHz readers you can plug into your phone… if only they could write!
There is the Keysy, If only it had a more suitable antenna for xSeries, But It would be interesting to see if it could read a “New” LF Flex?, I will try this when I am out of Lockdown ( I’m currently separated from my FlexMT ), Even if it works to read, it would be a pity we wouldn’t be able to write with it, because it uses a proprietry write method and will only write to Keysy products 
The Blue cloner would be awesome IF it didn’t write it’s stoopid password, it had a more suitable antenna, and could write to HF implant(s)
A while ago there was mention of a DT reader / writer project, but it never eventuated, The market would likely be too small to make it viable.
Paraphrasing Amal here ~“We have the Proxmark, that will do what we want, we would be better of spending time and money elsewhere”~
I am really hoping that the Flipper ,that, as well as reading HF and LF, it will be capable of writing also.
In my opinion, the Holy Grail of a what I want:-
HF & LF, small form factor, easy to use, basic interface with expansion to Phone App, and then add the other functionalities ontop 