Long-range and hard-hitting, eh? First stop then is probably a Pillager, which combines elephant-hide armor, twin Gauss rifles, and even a handful of jump jets to create a tough and surprisingly mobile long-range 'ow' platform.
Beyond that, I'm more mobility-minded personally, so anything that can't hit about 5/8 (or at the very least 4/6/4) tends to stay at home for me- which means mediums and fast heavies are where I live. It's amazing how handy jump jets can be for putting your sniper Mech up high by hopping up on a hill- or quickly finding a way back down in case things go pear-shaped.
Another couple of suggestions:
+Vehicles. Don't discount a tank because it's not all awesome and leggy. Heavy-hitters like the terrifying Alacorn and its trio of Gauss rifles, the lowly LRM Carrier, etc. can change the course of a battle quickly with a well-placed salvo. There's also fast-movers that can hit surprisingly hard- if you have interest in House Liao gear, the Regulator is possibly the finest fast-strike unit in the Inner Sphere, faster than a Locust and hitting with a turret-mounted Gauss rifle. Either get some, or at least be very concerned about an enemy having them. And of course, if you want a close-range bodyguard for your long-range platforms, a Demolisher is simply the best way out there to tell a snooping scout to go the hell away- twin AC-20s is a pretty clear message to send.
+Light Gauss. (NOTE: This weapon is from about 3060 onward) People often eschew them (or outright hate on them) here, because it's a big, heavy weapon that only does eight points of damage. And that IS unfortunate. But it also reaches out to ranges that many weapons can't even reply at, and that also means its medium range bracket starts a lot sooner than most- so you're hitting for eight points when the enemy can't reliably respond. But only eight points, right? Yeah, that's why you never deploy ONE. It's a Marik-made weapon, and Marik is almost always about working with a team to bring down an enemy- so you're firing SEVERAL of these things in conjunction. It works well in that regard- really, anything with an AC-10 often could only be improved with an LGR installed.
+OK, ok, so the Clans eat babies and are grown in coffee cups, whatever. Doesn't mean having the occasional salvaged tech isn't fun now and then. Don't go overboard with it, but a little here and there can be fun. I suggest the Mad Cat Mk.II for a big beefy nightmare, with twin Gauss, twin LRM-10s, a quartet of medium lasers, and jump jets on a 90 ton frame (and readily available in the Inner Sphere to anyone willing to rub coins together). Another good one from recent years is the Wolf Clan's Sun Cobra, which is little more than dual-Gauss strapped to an engine with a targeting computer. Not very quick, so I'm a little shy to use them (also it's Wolf-made, so I hate cleaning all the dog hair out of the cockpit), but in a defensive role a Sun Cobra or two can be a sobering thing to deal with- yes, it's post-Jihad tech, but many Omnimechs can easily be made to ape this configuration. Another to think about- one that I personally have a colorful history with- is the Bane/Kraken. An Ultra AC-2 is a pretty anemic weapon. TEN of them, however, adds up alarmingly quick, particularly when backed by other long-range units like that Sun Cobra.
+One more thing. I play Marik when I'm not a Clanner, and part of that is because my longtime love of the Orion knows no bounds. It's not the fastest unit, the toughest armor, nor the most perfect weapon layout, but somehow it always seems to all add up to more than the sum of its parts. They can fight at any range modestly well, they take a beating that seems unlikely for its size, and somehow find ways to win fights where other similar-sized machines wilt. Others may (and likely WILL) disagree with me, and they're welcome to- for me, an old ON-1K (or in more recent years a 2M) will absolutely dominate a battlefield given the chance, fill almost any role I can throw at it, and hobble home in victorious tatters.
