It's a cute way of saying thank you.
person #1: Harro, i got you a gift for your birthday
person #2: Tanku ^^
To be incredibly good at something.
Billy: Did you see Jill run the 100m sprint?
Bob: Yeah, she's so tankus, she beat everyone by like 5 seconds!
Abbreviated and informal version of "thank you" typically used in written communications such as e-mail or SMS text messaging.
Jane: cn u pk up sm apples @ the spmkt?
John: gt em ths mrning
Jane: o, tanku
A living example of inter-species breeding.
One such case currently resides in Canada. While the guesses as to which species it was run close to infinite, most scientists suspect he was conceived during a wild party involving a herd of buffalo and his crack-addicted mother.
Christ, you tankus... They really ruined a perfectly good rectum when they put teeth in your mouth.