Safe ways to remove sensitive data?

sufdisk -ldd if=/dev/urandum of=/dev/sdX

The best practical way without James Bond gear? Bench grinder. Make sure it's all dust. Wear a filter.

This is the worst translation I've ever seen.

More people have drills than benchgrinders. If he wants to be super cheap, all he really needs is a torx bit to open it up and a rock to smash the platters. There's a nice magnet in there too.

Drilling it or setting it on fire won't elimintate the magnetism of all the 1's and 0's on the drive. It could still feasibly be recovered with special tools that ignore disk sectors. You have to do and then shred the disks with a grinder down to the last peice of steel if you want to be sure. But in reality you shouldn't be placing that data on a modern computer if you care so much as to securely destroy it.

Does putting CDs in a microwave effectively get rid of their content?

No because the same principle as the magnet for hdd's apply. If you don't destroy every single 1 and 0 it can still feasibly be recovered by extreme autism. Shred it into tiny fragments or delaminate it to the point you have melted it into slag.

Use full diek encryption, or at least encrypt the partition that has confidential data, like /home and /tmp (but you're better off to have /tmp as a ram disk). Swap partition also, if you have one - OpenBSD encrypts this by default since like forever.
Then when it's time to get rid of disk, format every partition, and then overwrite every single disk block with 'dd' (that'll cover also the boot sector and partition tables).

...

This, but modify DD a bit for better performance and confirmed writes (also, shows progress):

dd if=/dev/urandom of=/dev/sdX bs=1M status=progress iflag=nocache oflag=nocache

Also for any windowsfags reading this you can secure erase even easier, format the disk so it's got nothing on it, then do:

cipher.exe /w:driveletterhere:

Fills up the disk with zeros, then all 1s, then pseudorandom crap.