As you may know, Hammerfall have made quite a few covers, enough to release a compilation CD made entirely of covers. Plus, there's "My Sharona" on the new album. So, which one do you prefer? Personal favorite is "Ravenlord", ever since I first heard it it pops into my head quite often, and I enjoy listening to it as much as the first time.
The songs listed, are also some that I like more than the other, and I obviously had to make a choice. If a cover you like isn't listed, please name it.

No doubt Man On The Silver Mountain, ist good originaly and covered to, also Judas Priest cover is good , but I prefere Rainbow, othgers are good to, but I dont know those well to judge

It's ironic you missed imo the best 3 covers they ever did: Head Over Heels, Detroit Rock City and Back to Back. the first 2 are pretty much modern heavy versions of classics. Ravenlord is pretty good too though Cans' voice sounds weird on it.

if i had to choose between one of those 3 it's Head over Heels. i even prefer it to the original(same with Detroit Rock City)

Man on the Silver Mountain is their best cover by far. The rest, in my opinion, ranged from decent to good. Also, I think their cover of I Want Out sucks. xP