I just used, without thinking, the word "забывало" to mean "a person who forgets things all the time". When I started to think about it, I couldn't remember having heard the word, nor could I find such usage in dictionaries or on the internet. Somehow it still sounds good to me - what do you people think? Is it correctly formed, understandable and idiomatic?
It sounds like a nonce word, but is quite understandable in that meaning. Maybe something like "забывала" (запевала, заводила, зазывала, вышибала), "забывальщик" or "забывальщица" when used between friends would sound less offensive since "забывало" reminds of such typical words as "быдло", "хамло", "мурло" etc. However, the difference between "забывало" and "забывала" is only noticeable in written form.
-ло holds its own basic meaning when it is added to the verb root: tool for doing; instrument, or agent. For example,
мыть - мыло, шить - шило, сидеть - седло, править - прав́ило,
хлебать - хлебало, крыть - крыл́о, покрывать - покрывало, ...
Whenever you may wish to write as an author, who intented by that suffix
-ло to make a new word, you should bear in mind that
мыло забывало покрывало (word play) are the past tense of a verb in the neuter gender of a doer, too.
When we are faced with a case of homonymy with two previous well-known meanings, we shall solve the problem with ambiguity, but in the case of just the newborn word the case of homonymy exists only in our mind, and we should clearly tell the reader what it is. Most certainly a reader will take a meaning by operating unconsciously, thus will stick by the well-known form of a verb. On this course you will not achieve the goal, but reader would be forced to read again the same phrase in attempts at getting to know.
When an author don't have a willingness to run the risk to be a pioneer with that new word, he/she may use in Russian
a) a capital letter to denote a proper Name
Ты такой Забывало. (mood: informal, familiar; not agressive);
b) doublling for a letter, when there is a need for a temporary "common name"
c) make similar with surnames
Тебя звать не Забывайло, часом? (mood: sarcasm, familiar; in a "correcting" or "accusatory" way)