At our work most of the non-Finnish speaking adopt at least three Finnish words into their everyday language:
Pulla - bun. Every Friday at afternoon coffee break we have pulla too. It's not always very orthodox pulla (pastry made out of sweet wheat dough that is expanded by using yeast), but something sweet though.
Mökki - summer cabin. Almost everybody has it, and people drive there on every summer weekend. Mökki is usually quite primitive piece of real estate in the middle of nowhere, often without electricity and without running water. That's where most people reach the zen.
Nakki - small sausage or a task. Kids prefer to grill nakkis instead of real sausage. They even cut the both ends of the nakki to make it "laugh" (the cut ends of the sausage kind of buckles when you grill it). Nakki is somewhat traditional food on New Year's Eve and on 1st of May. Nakki is also a task that you can give to someone - a delegated action to be taken.