In general, this year's (PC/FPS) games I'd pick as being worth a lookin are:

* Deus Ex: HR. This year's GOTY for me. Amazing single-player storyline, and it's truly open-approach as far as levels are concerned. I played the game almost entirely stealthily (ie. finding air conditioning ducts to hide in and making extensive use of augmentations which showed enemy patrols' FoV in order to avoid detection), but you could approach it completely differently and gun down every last dickhead guard. In a year where Portal 2 had clenched my favourite spot, this did incredibly well to claim it.

* Portal 2. Valve, Portal, `nuff said. I didn't think it was as good as the first one (there were a lot less twitch-esque puzzles, due to the PS3/360 not being able to support the rapid mouse movements a PC does), but still an excellent game.

* Battlefield 3. The whole BF3/MW3 thing is the most ridiculously hyped up marketing exercise in existence, but the multiplayer here is still Battlefield, and still solid. Might not be your cup of tea, but definitely fun for a hoon.

* Tribes: Ascend. Still in beta, and still being actively tweaked (thankfully, as the balance is currently nowhere near correct). Still, it's undoubtedly Tribes: fast, airborne, and team-oriented. Woot woot.

* Dead Space 2. My favourite horror/FPS mashup. It's not so much scary as it is shocking; generally, you get less of a fright (unlike Amnesia, which is deeply unsettling), and more of an OH FUCK style surprise. Really, really glad EA kept this franchise going, but I imagine after one more round I'll be over it (sadly).

Also, if you play nothing else from the indie establishment, Bastion is amazing. If I was to recommend only two games from this year, for me, they'd be Deus Ex: HR, and Bastion :).

In terms of other tactical games you might like, I don't typically play that genre so can't be a good recommendation engine unfortunately. Company of Heroes, while an RTS (and long in the tooth now), focusses more on local tactics than it does traditional RTS trappings (ala Starcraft 2). Thanks to the recent failure of CoH: Online, it's had a bunch of balance changes backported and is currently undergoing somewhat of a rejuvenation :). The Dawn of War II series is RTT (tactical; there's no basebuilding) but the online is so hardcore most have been turned off it by now.

Edit: If you like hardcore tactical multiplayer, you might want to check out "Battleground Europe". Oldest online multiplayer game still running, as far as I know. It has its rough edges, and certainly can't compete in the graphics area, but the realism when it comes to weapons modeling is the best I've seen. Not to mention the skills you find in the longtime players. Check out the top anti-aircraft gunners (like http://www.youtube.com/watch?v=N_eeYikGjjw).