I have a Bushnell one that seems to work well i picked up for $39 at a local gun shop. It seems to work well and get me in the ballpark before heading to the range.
I just wish it would go under .22 and fit .17hmr but i think i can make an arbor for that easy enough.
i got one at academy that slides down the end of the barrel and you use rubber grommets for different bore sizes. i don't recommend it at all.
here is what got me. on the instructions it states that there is a wind-age and elevation screw to adjust the laser! what did i buy the thing for if i have to first sight it in?!
1+ Walmart I save even more money , I have a friend who bought the WalMart laser job under 40 bucks , I borrow it . Several arbors and a better sytem than many expensive ones . It has bore sighted about 20 rifles so far .