Depends on what you're going for.
More tactical or target shooting?
Your options are endless.
For tactical stuff: Falcon Menace 4-14x 44mm MP20 metric would be a good fun value scope with an excellent list of features. But... then you can go upscale from there. Leupold MKIV, NF, S&B etc etc.
For target shooting there's some overlap, but the magnification is usually higher. The best bang for the buck right now in my opinion is the Zeiss Conquest line. After that NF, and the rest.
With the rare exception, good glass is expensive. If you want to go all out you can easily spend twice as much as the rifle. I try not to do this, but if the rifle is one that really shoots.... well it's easier to justify
My recommendations for the Tikka tactical:
1) S&B and comparable $$$
2) Night Force -Considered a good value for the upper end scopes-
3) Leupold Mark IV for tacticool non varible scope only
4) Zeiss Conquest -excellent value, especially for target/varmint shooting when not worried about being "tacticool"
5) Leupold VXIII target/hunting varible scope
6) Falcon Menace - Tacticool while still being thrifty. Excellent reviews, good glass, great feature set for the price.
7) Burris scopes. Well made, good glass, reasonable price.
The 6mm BR site has a fantastic scope review section. There's some stuff missing but it's definately a must read before making any purchases.
The night force would be my overall pick if I could justify the extra cost.