“可是”, which means ‘but’, was my filler word in Chinese, until Eva started making fun of me I started to change it. Every time I said 可是 she screamed “BUT!!!!!”

Like:

• “It’s not perfect 可是 we can still go there”
  • “BUT!!!!!”
• “This thing is that 可是 that thing is this”
  • “BUT!!!!!”
• “It’s raining 可是 it’s alright”
  • “BUT!!!!!”

Your best language partner is someone who cares about you but not about being polite.