lol i like the last idea
i suggest a 2x4.
So, how old are you then?
14
and i found a thread with many ideas
i guess the search button really does work
for those interested: How can I convince my parents to let me buy a $400 unicycle?
Awesome! I’m glad you figured this out, many new forums members post blindly without even considering searching. You seem bright enough that you will figure out your situation just fine.
Show your parents this and suggest that they learn as well, unicycling is not just for teenagers doing tricks, just see how many of us old f***s there are.
Show your old man some of MuniAddict’s vids and tell him if he learns to uni he’ll look like Terry when he’s 52, if he’s not there already that is.
sit around doing nothing, all the time.
they will tell you do do something, make that something unicycling.
just say “id like this unicycle” (show them whatever uni), show them some videos and say it will help your balance, keep you fit, improve your co-ordination and self confidence and get you out the house. that would be enough surely, otherwise go and buy a cheap uni yourself, that way they cant say no lol:D
Many successful people unicycle, such as this man, who alas died when the space shuttle Columbia went down (might not want to mention that):
Also, I’m not sure, but didn’t Rumsfelt (spelling?) unicycle once upon a time? Again, bad example 
my mum came to visit today and saw my just out the box new uni that cost little over £200 and ranted about how it was money i should be… blah blah blah.
i said somthing very similar to the above and she just gave me one of those looks that mums do and shook her head and said “well i suppose it looks nice and i do like those blue marball things in the tyre”. she was on about the rim tape showing through the rim, not got a clue.
if you want one just get one!
Good excersize and you dont wanna become the fat kid from Willy Wanka!
Do they let you ride a bike? If they do then tell them it is exactly the same as learning to ride a bike. You might fall off every once in a while, but would you let that stop you learning a very valuable life experience. Who didn’t learn to ride a bike when they were little.
don’t ask them to let you unicycle, tell them to let you unicycle
Bike falls are usualy worse, more speed + handle bars.
It can’t fail, trust me i’m a unicyclist 
ask them. you’ve got plenty of good reasons, but won’t know if you’ll actually need them until you ask.
Maybe if you get a part time job and can pay for it yourself from your earnings it may impress them that you are goal oriented. I’m 46 and the only way I can support my hobby habits is by doing side work so it doesn’t remove funds from our household budget.
id still go with a trusty 2x4. but thats just me. 
Tell them you want to take up skydiving. They’ll tell you it’s too expensive and dangerous. Then you say “So how about unicycling?”
Seriously, probably the best way is to get the unicyle yourself. I would guess they probably don’t care so much if you unicycle, but don’t want to go spend a bunch of money on it, either.
If you have CraigsList in your area, maybe run an ad looking for a free unicycle. Couldn’t hurt. There’s plenty of them stashed away unused.
Hahahhahahahahaha zing
First of all do your parents watch any TV? If so, nuff said.
Secondly, if your parents actually do think unicycling is a stupid waste of time, remind them that stupid wastes of time are an essential part of life. Without them all the rest would be quite overwhelming.
And for the record, I am a parent. (How successful though depends on whom you talk to.)