Chinese has
甭 Beng, which is a quick pronunciation for 不用 BuYong
别Bie, which amongst other things, is a quick pronunciation for 不要.
The French language is notoriously conservative, although e.g. “Qui est-ce qui” can be substituted with just “Qui.” (roughly, “who is it who” vs. “who”). “Qui est-ce que” and “Que est-ce que” can also be replaced with inversion. But these are official usages and not slang.
Some contractions like p’tit occur, and especially so in French-based languages or dialects like pidgins.
On the other hand, internet idiots use the “longcut phrase” “should of” instead of “should’ve.”
double post
In common Brazilian Portuguese, many people will convert a phrase like O que você está fazendo? (“What are you doing?”) into Que cê tá fazendo? (same thing, but more like “What’s up?”), chopping part of você (you) and part of está (3rd* person of the non-permanent “to be”).
And você is already a contraction of the archaic vossa mercê.
- the “you” used by most Brazilians is really conjugated as 3rd person. Rarely will a Brazilian use “tu”.