SDR-9K Venom - The Spider grows up. It has a ridiculous 12 single heat sinks and less armor than a Locust, but those 4 MPLs are deadly when used correctly: jump in 8, fire all 4, jump out, cool off; repeat. The SDR-9KA Venom has lower heat and plenty more armor at the cost of 1 MPL, and is perferred against pulse-capable opponents.
TMP-3M Tempest - A versatile weapon mix and adequate heat sinks under heavy armor make this jumper a winner. I also include it here because it makes a wonderful mech for training in both Level 2 and general BattleTech combat: it has ballistic, missile, and energy weapons; it jumps; it has ammunition to keep track of; it has special to-hit number modifiers like the Gauss' minimum range and the LPL's -2 bonus, it's missing a hand actuator, which makes carrying and punching harder; its weapons have mismatched ranges, which calls for combat judgment in jockeying for position; and it overheats when firing everything and jumping, necessitating good heat management. Too expensive to train Warriors, but ideal for training Players.
FLC-8R Falconer - The Falconer is useless. That being said, I absolutely love it, and will choose it every time I get the chance. It doesn't have the spare weight to mount heavier guns, nor does it have the heat sinks to effectively use what it has. On the other hand, it's the fastest mech of its size, a great jumper, and well armored in most places. It has endurance, and its guns are multi-ranged and useful, if few. The Falconer is the biggest example of an anecdote from Sun Tzu's Art of War: in a contest in which the combatants are ranked according to ability, match your best against the enemy's second-best, your second-best against his worst, and your worst against his best. You'll win two times out of three, only your worst will be lost, and the day will be yours. The Falconer belongs to the former two categories. Send it against slower and inferior mechs and they're meat. Use it to intercept a flanking maneuver, or to tie up enemy fire support. Basically, use it like a Spider or Venom, but alone against big targets. Remember, though, that the Falconer also exemplifies the philosophy that produced the Battlecruiser (speed and armor of a cruiser, firepower of a battleship) in WWII: it can outrun whatever it can't outgun.
ALB-3U Albatross - The name fits. It can do everything, but it excels at nothing. It's another great player-trainer, and it's always a good choice when you don't know the enemy or the terrain, since it can cover just about every possible contingency, though it is ammunition-dependent with XLs.
MR-5M Cerberus - This is the ERPPC variant; up close and personal, that Gauss and those 6 MPLs can really hurt. It's over-heat sinked (for once), and I wish they'd drop a DHS or two for armor instead; an XL mech meant to fight close and dirty needs lots of protection. Still, it's a vicious beast, especially when used to hunt down pesky Heavy and Medium mechs that are trying to jockey for position. It also makes a great guardian for slower mechs, since it can help out at long range until lighter mechs (Phoenix Hawks, Venoms, etc.) approach with intention to harass; at that point, those MPLs are brought to bear, and the -2 bonus negates the to-hit penalties built up by fast-moving units. A Venom is a great annoyance mech, but when it jumps in range for its own guns, its paper-thin armor will be chewed to pieces by the MR-5M's pulses.
NG-C3A Naginata - What can I say? The perfect fire-support platform. Too bad nothing in 3055 came equipped with C3 Slave units. CASE would've been nice, but that's nitpicking.
Matt's favorite FASA 'Mechs: 3058
LNX-9Q Lynx - Actually, all Lynxes are good mechs, though the Q and R are slightly preferred; the C runs cooler, though. I wish they'd mounted pulses, but otherwise, this is a Wolverine variant, to be used the same way. Note that without pulses, the Lynx will stay grounded more than the Wolverine to keep its to-hit numbers low.
CTS-6Y Cestus - Nothing special here, just solid, armored performance. Heat is balanced perfectly (a FASA miracle!), it covers all ranges, and the ammunition supply is adequate. Its only real flaw: the torso-mounted Gauss in an XL mech.
DGR-3F Dragon Fire - As with the Cestus, FASA finally got sensible. This is an all-range, multi-purpose heat balanced mech with excellent armor. No major flaws, though it does rely heavily on ammunition.
MTR-5K Maelstrom - A Zeus shouldn't move this fast. It has too few weapons, but it can handle all its heat and its speed and armor are great. It makes a wonderful fast sniper, providing long-range fire support, plus it's perfect as an interceptor: Someone charging your artillery? Need to blunt the enemy's advance, but don't have any big mechs to throw in their path? Send this! It's a ground-based Falconer, with more armor.
LGB-7V Longbow - Unlike some mechs that do everything but do nothing well, the Longbow does two things excellently: provide ranged fire support and spew out nasty close-range barrages. With its ranged weapons (with Artemis IV and lots of ammunition), ample heat sinks, massive armor, and array of pulses, it matches the Cerberus' profile, though its lower speed makes it better suited to guarding formations of fire support mechs than to chasing down pesky mediums.