I thing slaking would be a nice addition to my team, but I cant find a Slakoth.
By using the hoenn sound sounds on route 25 by bill's house on a Wednsdays.
There's a Headbutt tree on route 25 with them in. There is only one tree though.
If you need help it's at the bottom of this http://www.psypokes.com/hgss/headbutt.php